It should be any quest that awards Valor, you're saying you earned valor but still not been awarded the achievement?
I tried completing a daily quest and I am not VP capped. I have opened multiple tickets and been told that "there's no record of my ever having been on that quest." I asked the GMs to check when I completed the previous quest and the VP I have earned since that point. They said that the previous quest complete date is no longer in the logs, indicating I completed it more than 3 weeks prior. I pointed out that I've earned at least 8-10k VP since 5.2 (cannot remember how many I had when 5.2 dropped) BUT was told that it doesn't matter as I "never" was on the quest line.
I am so furious to be treated this way by blizzard. Even if that were true and I had stupidly forgotten to pick up the quest (Which I assure everyone I did not!) to be punished by adding another 3 week wait onto the previous 6-8 week VP check, is an abysmal way to treat paying customers.
If you're unhappy with how your issue was handled you should email CSFeedbackEU@blizzard.com, the issue will then be reviewed by the Senior Game Masters who will make sure everything was handled correctly.