Neither log message relates to an integrated wiki page not showing over, say, a forum thread. I don't know what version you have before you upgraded. It is possible that your old version was before some new settings were added.
See VaultWiki Admin Panel > Settings > Miscellaneous:
- Allow Wiki Content Integration
- Wiki Content Integration Locations
If these settings are correct, please let me know what other steps you have taken to show wiki content above the forum pages you are testing.
As for the Fatal Error, it is unfortunately a bit crazy (it claims a core XenForo class does not exist), so you would need to know what you were doing when the error was triggered, the URL that triggered it, and how to reproduce.