Just found out the hard way and to the dismay of my party at the end of the Goblin Fort quest that my ring of knock wasnt working.

Also but after using a weapon with vampiric regeneration, for several encounters, I failed to notice any increase of hp. Will test it out properly soon and confirm it here.

Vampiric regen is finicky. You may get +1 HP once every 3-5 hits.

Vampiric Regeneration is: vampiric regeneration 1x / round, I believe.

This is an engine-level issue, pointed out in an NWNWiki article: http://www.nwnwiki.org/Vampiric_regeneration

I'm not sure how Knock "wasn't working". I know I've seen it work before, so I need to know more.

I tried a ring of knock before and it did nothing. The ring disappeared after the use but none of the locks opened. The spell works but I haven't seen the ring work.