Ranked up to level 15, I have enough parts, but can't level up my cards

I had a similar issue with the initial upgrade.  The card level requirement and class level requirements were met, but the upgrade was locked.  The trick is... your class level requirement needs to be ONE LEVEL HIGHER  than what it says.  So.. for the first upgrade... it says you need class level 10... but in reality...the upgrade only UNLOCKS when you reach level 11.   Thus, in your case, if the class level requirement says 15... when you turn level 16 the unlock will occur.  Hope this helps!

Unfortunately that is not the issue, the game is showing that I meet the requirements.  See the attached screenshot.

Thank you for the advice.  Since you posted that, I've been trying to get to level 16. Halfway there, I'll post an update when I get there.  Thanks again!

@sday2016 Hi, do you still have the issue today?

It looks like there may have been a temporary issue with some folks, but if you still can't upgrade that's interesting to know. I'd also be interested if you've hit rank 16 yet.

Update:  I reached level 16 and I was able to upgrade everything.  The first user to respond was correct.  Thank you.  Although that problem is solved, the milestones I earned but can't claim are still there and now I've earned new ones I can't claim......

Thank you for the update and marking the solution. 

The milestones issue is still affecting folks, hopefully it won't be too much longer now. 

Cheers.