Cannot Upgrade to gitlab ce 16.6.0

p_ci_builds table does not exist in the database which is causiing the gitlab server show 500 error but it works on 16.5.2 without any issue though the table doesn’t exists

The issue is raised from 15.11.x series

You can use Upgrade Path to check what the exact Upgrade Path should be depending on the version you are coming from and if you want to do this downtimeless or not.

Also check Deprecations by version and Version-specific upgrading instructions.