5.2 to 5.7 and forum is broken

I upgraded from 5.2 to 5.7 and all is fine, except my forum, which no longer shows posts. I followed some advice, and parsed some php code to determine if it was reading the correct MySQL table, and it appears that it is not. But, I did not know how to fix it. Problem is, I cannot even find that thread now!

Currently the forum is offline.

If anyone knows how to fix this problem, which I believe is related to Drupal looking up the incorrect table in the database, please let me know how to fix it!

Cheers

Jon.