Did some more due deligence on the error reported in es.Log file. That led to deletion of temp files in sonar folder. Post trying that again getting the same error, but with no errors logged in es.log file.
ES.Log File details below :
2020.05.15 11:31:39 INFO es[o.e.n.Node] initializing …
2020.05.15 11:31:43 INFO es[o.e.e.NodeEnvironment] using [1] data paths, mounts [[OSDisk (C:)]], net usable_space [202.5gb], net total_space [476gb], spins? [unknown], types [NTFS]
2020.05.15 11:31:44 INFO es[o.e.e.NodeEnvironment] heap size [990.7mb], compressed ordinary object pointers [true]
2020.05.15 11:32:01 INFO es[o.e.n.Node] node name [sonarqube], node ID [skrO64g9Ry2VYdwdam9yGA]
2020.05.15 11:32:01 INFO es[o.e.n.Node] version[5.6.3], pid[10072], build[1a2f265/2017-10-06T20:33:39.012Z], OS[Windows 10/10.0/amd64], JVM[Oracle Corporation/Java HotSpot™ 64-Bit Server VM/1.8.0_201/25.201-b09]
2020.05.15 11:32:01 INFO es[o.e.n.Node] JVM arguments [-XX:+UseConcMarkSweepGC, -XX:CMSInitiatingOccupancyFraction=75, -XX:+UseCMSInitiatingOccupancyOnly, -XX:+AlwaysPreTouch, -Xss1m, -Djava.awt.headless=true, -Dfile.encoding=UTF-8, -Djna.nosys=true, -Djdk.io.permissionsUseCanonicalPath=true, -Dio.netty.noUnsafe=true, -Dio.netty.noKeySetOptimization=true, -Dio.netty.recycler.maxCapacityPerThread=0, -Dlog4j.shutdownHookEnabled=false, -Dlog4j2.disable.jmx=true, -Dlog4j.skipJansi=true, -Xms1024m, -Xmx1024m, -XX:+HeapDumpOnOutOfMemoryError, -Delasticsearch, -Des.path.home=C:\SonarQube\sonarqube-7.6\elasticsearch]
2020.05.15 11:32:13 INFO es[o.e.p.PluginsService] loaded module [aggs-matrix-stats]
2020.05.15 11:32:13 INFO es[o.e.p.PluginsService] loaded module [ingest-common]
2020.05.15 11:32:13 INFO es[o.e.p.PluginsService] loaded module [parent-join]
2020.05.15 11:32:13 INFO es[o.e.p.PluginsService] loaded module [percolator]
2020.05.15 11:32:13 INFO es[o.e.p.PluginsService] loaded module [reindex]
2020.05.15 11:32:13 INFO es[o.e.p.PluginsService] loaded module [transport-netty4]
2020.05.15 11:32:13 INFO es[o.e.p.PluginsService] no plugins loaded
2020.05.15 11:33:18 INFO es[o.e.d.DiscoveryModule] using discovery type [zen]
2020.05.15 11:33:29 INFO es[o.e.n.Node] initialized
2020.05.15 11:33:29 INFO es[o.e.n.Node] starting …
2020.05.15 11:33:49 INFO es[o.e.t.TransportService] publish_address {127.0.0.1:9005}, bound_addresses {127.0.0.1:9005}
2020.05.15 11:33:59 INFO es[o.e.m.j.JvmGcMonitorService] [gc][23] overhead, spent [301ms] collecting in the last [1s]
2020.05.15 11:34:01 INFO es[o.e.c.s.ClusterService] new_master {sonarqube}{skrO64g9Ry2VYdwdam9yGA}{2tpgFLBKQ3CnJySu6gkRXA}{127.0.0.1}{127.0.0.1:9005}{rack_id=sonarqube}, reason: zen-disco-elected-as-master ([0] nodes joined)
2020.05.15 11:34:02 INFO es[o.e.n.Node] started
2020.05.15 11:34:05 INFO es[o.e.m.j.JvmGcMonitorService] [gc][29] overhead, spent [438ms] collecting in the last [1.5s]
2020.05.15 11:34:32 INFO es[o.e.g.GatewayService] recovered [8] indices into cluster_state
2020.05.15 11:36:28 INFO es[o.e.c.r.a.AllocationService] Cluster health status changed from [RED] to [GREEN] (reason: [shards started [[metadatas][0]] …]).
2020.05.15 12:01:32 INFO es[o.e.n.Node] initializing …
2020.05.15 12:01:42 INFO es[o.e.e.NodeEnvironment] using [1] data paths, mounts [[OSDisk (C:)]], net usable_space [202.5gb], net total_space [476gb], spins? [unknown], types [NTFS]
2020.05.15 12:01:42 INFO es[o.e.e.NodeEnvironment] heap size [494.9mb], compressed ordinary object pointers [true]
2020.05.15 12:02:10 INFO es[o.e.n.Node] node name [sonarqube], node ID [skrO64g9Ry2VYdwdam9yGA]
2020.05.15 12:02:10 INFO es[o.e.n.Node] version[5.6.3], pid[14768], build[1a2f265/2017-10-06T20:33:39.012Z], OS[Windows 10/10.0/amd64], JVM[Oracle Corporation/Java HotSpot™ 64-Bit Server VM/1.8.0_201/25.201-b09]
2020.05.15 12:02:10 INFO es[o.e.n.Node] JVM arguments [-XX:+UseConcMarkSweepGC, -XX:CMSInitiatingOccupancyFraction=75, -XX:+UseCMSInitiatingOccupancyOnly, -XX:+AlwaysPreTouch, -Xss1m, -Djava.awt.headless=true, -Dfile.encoding=UTF-8, -Djna.nosys=true, -Djdk.io.permissionsUseCanonicalPath=true, -Dio.netty.noUnsafe=true, -Dio.netty.noKeySetOptimization=true, -Dio.netty.recycler.maxCapacityPerThread=0, -Dlog4j.shutdownHookEnabled=false, -Dlog4j2.disable.jmx=true, -Dlog4j.skipJansi=true, -Xms512m, -Xmx512m, -XX:+HeapDumpOnOutOfMemoryError, -Delasticsearch, -Des.path.home=C:\SonarQube\sonarqube-7.6\elasticsearch]
2020.05.15 12:02:25 INFO es[o.e.p.PluginsService] loaded module [aggs-matrix-stats]
2020.05.15 12:02:25 INFO es[o.e.p.PluginsService] loaded module [ingest-common]
2020.05.15 12:02:25 INFO es[o.e.p.PluginsService] loaded module [parent-join]
2020.05.15 12:02:25 INFO es[o.e.p.PluginsService] loaded module [percolator]
2020.05.15 12:02:25 INFO es[o.e.p.PluginsService] loaded module [reindex]
2020.05.15 12:02:25 INFO es[o.e.p.PluginsService] loaded module [transport-netty4]
2020.05.15 12:02:25 INFO es[o.e.p.PluginsService] no plugins loaded
2020.05.15 12:04:57 INFO es[o.e.d.DiscoveryModule] using discovery type [zen]
2020.05.15 12:05:42 INFO es[o.e.n.Node] initialized
2020.05.15 12:05:42 INFO es[o.e.n.Node] starting …
2020.05.15 12:06:03 INFO es[o.e.t.TransportService] publish_address {127.0.0.1:63600}, bound_addresses {127.0.0.1:63600}
2020.05.15 12:06:08 INFO es[o.e.c.s.ClusterService] new_master {sonarqube}{skrO64g9Ry2VYdwdam9yGA}{y_lOLqc6Su227OgL_FbgOw}{127.0.0.1}{127.0.0.1:63600}{rack_id=sonarqube}, reason: zen-disco-elected-as-master ([0] nodes joined)
2020.05.15 12:06:15 INFO es[o.e.n.Node] started
2020.05.15 12:07:07 INFO es[o.e.g.GatewayService] recovered [8] indices into cluster_state
2020.05.15 12:07:07 WARN es[o.e.c.s.ClusterService] cluster state update task [local-gateway-elected-state] took [32.3s] above the warn threshold of 30s
2020.05.15 12:10:57 INFO es[o.e.c.r.a.AllocationService] Cluster health status changed from [RED] to [GREEN] (reason: [shards started [[metadatas][0]] …]).
2020.05.15 13:10:58 INFO es[o.e.n.Node] initializing …
2020.05.15 13:11:01 INFO es[o.e.e.NodeEnvironment] using [1] data paths, mounts [[OSDisk (C:)]], net usable_space [202.5gb], net total_space [476gb], spins? [unknown], types [NTFS]
2020.05.15 13:11:01 INFO es[o.e.e.NodeEnvironment] heap size [494.9mb], compressed ordinary object pointers [true]
2020.05.15 13:12:21 INFO es[o.e.n.Node] node name [sonarqube], node ID [skrO64g9Ry2VYdwdam9yGA]
2020.05.15 13:12:21 INFO es[o.e.n.Node] version[5.6.3], pid[16380], build[1a2f265/2017-10-06T20:33:39.012Z], OS[Windows 10/10.0/amd64], JVM[Oracle Corporation/Java HotSpot™ 64-Bit Server VM/1.8.0_201/25.201-b09]
2020.05.15 13:12:21 INFO es[o.e.n.Node] JVM arguments [-XX:+UseConcMarkSweepGC, -XX:CMSInitiatingOccupancyFraction=75, -XX:+UseCMSInitiatingOccupancyOnly, -XX:+AlwaysPreTouch, -Xss1m, -Djava.awt.headless=true, -Dfile.encoding=UTF-8, -Djna.nosys=true, -Djdk.io.permissionsUseCanonicalPath=true, -Dio.netty.noUnsafe=true, -Dio.netty.noKeySetOptimization=true, -Dio.netty.recycler.maxCapacityPerThread=0, -Dlog4j.shutdownHookEnabled=false, -Dlog4j2.disable.jmx=true, -Dlog4j.skipJansi=true, -Xms512m, -Xmx512m, -XX:+HeapDumpOnOutOfMemoryError, -Delasticsearch, -Des.path.home=C:\SonarQube\sonarqube-7.6\elasticsearch]
2020.05.15 13:13:05 INFO es[o.e.p.PluginsService] loaded module [aggs-matrix-stats]
2020.05.15 13:13:05 INFO es[o.e.p.PluginsService] loaded module [ingest-common]
2020.05.15 13:13:05 INFO es[o.e.p.PluginsService] loaded module [parent-join]
2020.05.15 13:13:05 INFO es[o.e.p.PluginsService] loaded module [percolator]
2020.05.15 13:13:05 INFO es[o.e.p.PluginsService] loaded module [reindex]
2020.05.15 13:13:05 INFO es[o.e.p.PluginsService] loaded module [transport-netty4]
2020.05.15 13:13:05 INFO es[o.e.p.PluginsService] no plugins loaded
2020.05.15 13:15:29 INFO es[o.e.d.DiscoveryModule] using discovery type [zen]
2020.05.15 13:16:04 INFO es[o.e.n.Node] initialized
2020.05.15 13:16:04 INFO es[o.e.n.Node] starting …
2020.05.15 13:17:15 INFO es[o.e.t.TransportService] publish_address {127.0.0.1:54029}, bound_addresses {127.0.0.1:54029}
2020.05.15 13:17:27 INFO es[o.e.c.s.ClusterService] new_master {sonarqube}{skrO64g9Ry2VYdwdam9yGA}{N1J834qsSka9eC9p7PAafQ}{127.0.0.1}{127.0.0.1:54029}{rack_id=sonarqube}, reason: zen-disco-elected-as-master ([0] nodes joined)
2020.05.15 13:17:27 INFO es[o.e.n.Node] started
2020.05.15 13:17:59 INFO es[o.e.g.GatewayService] recovered [8] indices into cluster_state
2020.05.15 13:21:17 INFO es[o.e.c.r.a.AllocationService] Cluster health status changed from [RED] to [GREEN] (reason: [shards started [[components][1], [metadatas][0]] …]).