In the top right corner of the webpage where my profile pic is supposed to be, it justed says "Avatar," then my username.  I tried clearing my cache and restarting my computer, but it's still a problem.  Is this a bug?    

I have had a selection of missing portraits ever since the servers switched over to WotC. Some characters just have black squares, others work fine. I am sometimes able to reset them but even then, the portraits don't show up on my character list, only on the sheet itself. Maybe I need to clear my cache?

Okay.  Glad to see that's it's not my computer or browser causing the problems, but might be a problem with D&D Beyond itself.