One note - if you go to the level select and pick the level in question, you do NOT get the quest for beating it. You have to beat ALL levels before it.
The quest really should read 'Beat levels 1-15', 'Beat levels 16-30', 'Beat levels 31-45'.
Or 'Beat THROUGH level 15', 'Beat THROUGH level 30', 'Beat THROUGH level 45'.
All quests work but as Olinser said you must play the level before 15, 30 and 45 also. So just play through the games. As every game on this genre: check youtube for guides if you want/need them.
@Knir white/black screens are often caused by ad-blockers, if you have one active, deactivate it.
Also some other "block" software, like parental control/safety internet-software, could cause problems.
But it could be a simple loading issue, a simple site-refresh may fix it.
And sometimes its a browser-related issue, try another browser and see if it work (this could really work wonders, recommended!).
I don't know what's been going on lately but not ONE single game has been rewarding the quests for me the last few days. I'm logged in but it's like the website isn't reading that I'm logged in. How do I fix this?
You played these games on different computers with the same account? And have you F5'd as well?
Some games, like "king of towers" only unlock their quests when I F5
Normally, sum tracks didn't have any quests problems as far as I know.