I posted pictures in your other thread that showed my seal was definitely working for trees (usually 1-4, I got 1-6 with seal), monster seeds (gobball seeds are 1-5, I got 1-8 with seal), and fish (piris give 1, but seal boosted it to 1-2. Seal does boost resources that would otherwise only give 1). And a couple of other people said their seals were working, too.
It is possible that this is a bug that is only affecting your character for some reason (crazier things have happened! ), but more people are saying their seals are working than not working, and we don't have any evidence from you yet!