I updated my Xbox app today morning and about an hour later I got this push notification....

Got my PC code at 9:16am. I just stared at my phone for it to get that push notification for an hour

Did you try clearing the Windows Store cache and then uninstalling/reinstalling? Not sure if it will fix it but it's worth a shot. As an interesting aside, my work computer here was not able to run several other apps as of this morning. I just got a notification
of an optional update pushed live and am installing that now. Maybe check your optional updates as well because these won't install automatically. As you can see, I run into these problems on occasion as well.

I think the notification pop- up problem is fixed because a while ago today, I play Zheroes and unlocked two achievements and I got the pop up notification. I though it was a fluke at first so I turn off my Xbox One and waited for an hour. After an hour
pasted, I started playing NS4 and I unlocked eight achievements with pop up notifications.

I don't know if this fix permanent or It just working today or it just working for my Xbox One, but think the problem with notification is finally over (until the next title update).

I played Valiant Hearts this morning and got 5 achievements but none of them showed up as notifications when playing the game. Tried NHL 15, same thing. Got the achievement but no notification for it. Noticed that my Gamerscore went up, that's how I found
out that I got the achievements. Anyone else having the same issues?

This just started happening today after the latest update. Before I always received the achievement notification popup instantly.

Yeah I played a game today after the update and everything was fine but when I got back on about an hour later all my dlc was gone, I even went to manage my games and add ons but nothing shows up.