VB.NET analysis became supported on the Community Edition with v7.7 of it’s language analyzer plugin, and v7.15 was the last version marked as compatible with SonarQube v6.7. You should be able to use the v7.15 of the analyzer free of charge on your v6.7 Community Edition instance.
(But don’t delay in planning your upgrade to Sonarqube v7.9 LTS!)