CDC breaks after patching
I recently patched some servers from SQL 2014 SP2 CU3 all the way up to CU10. The patching went fine, everything came back online and looked to be working perfectly. However, the next day I realised that the CDC Collection Job was not running. After much googling and trying to rebuild the collection job, I came across this blog from the MSSQL Tiger Team.
According to the blog, the problem only appears when the database is part of an Always On Availability Group AND you patch the secondary servers first – all of which was true for my scenario.
Running sp_vupgrade_replication, as suggested in that blog post, fixed the problem for me.