I have all the necessary skills needed to advance, but they keep telling me "we are pleased with your duties, but you don't fill out the requirements". What should I do? Should I keep doing duties or is there a problem?

Requirements means skills. So either you need to double-check that your skills are high enough, or the game's glitched.

If you're on PC, there's probably a console command around that - check UESP.

Are some of your skills fortified? Only base level counts.