Thanks for the reply , version 8.4.2 was installed in Azure App service as a web app about a year ago and its been on the execution with no issues until last weekend ,where azure instance had a restart which service to go down. on restart the web server couldn’t come back online with the above error. there were no changes with respect configuration or azure setup .so not sure what made the ES to have this error after a restart. we end up recreating new instance with version 9.0.0