Unable to Update Profile Picture

I am trying to update (i.e. change my existing) profile picture in Microsoft Teams.  I'm speaking about my personal picture, not the team picture.

I have tried every possible thing I can think to try to get this to work, and nothing works:

• I tried PNGs, JPGs, and JPEGs
• I tried a variety of sizes: 60x60 px, 100x100 px, 256x256 px, 512x512 px, with many other options as well.
• I tried using the Teams desktop app, the web browser app, the iPhone app, the iPad app.
• Within the web browser app, I have tried with Chrome and with Firefox.
• I have also tried updating my profile name at the same time, which I saw recommended in one community answer.

All of this fails to work.

Whenever I try with the desktop or web app, I get the error " There was a problem saving the photo. Please try again. "  Whenever I try with the iOS apps, I get the error "Error: We were unable to upload your image."  Obviously neither is helpful to understand what I should do to fix.

I've also encountered the exact same error if I merely try to remove the existing profile picture I have and go back to the generic colored text avatars (i.e. "There was a problem saving the photo ...").  Since I have a profile picture obviously this worked somehow before, but seems impossible to change now.

I am on a free version of Microsoft Teams, which (to my knowledge) is not linked to a larger Office365 account.

Please help!