It's kinda hard to get the quests you need to complete the quests tab when they are lower level than the ones you are able to get and also you don't know if on lower tiers there are quests you have not yet discovered.
Thanks for playing! So if you click the little tab on the board, you can switch to the different quest tiers so you can go back and complete the lower ones.
I will look into making it a bit clearer if you have not completed all of a tier. Currently, the only way to know is if you get the achievement for completing the Tier 1, Tier 2, etc quests, and that's not really apparent until you actually complete them. It's also something easily missed, as it's just a pop-up. Thanks for bringing that to my attention!