Azure DevOps profile pictures not displayed on boards

Question

We recently switched to  Azure DevOps. I successfully connected our tenant to DevOps, the profile pictures do not appear in all places. Most crucially, they do not appear on cards on boards. They do, however, appear in the top right corner and when configuring the team. Here's a screenshot showing the missing profile picture: 

Here's a screenshot showing the missing profile picture: 

and one showing the profile picture in settings: 

I waited for about a week. So I also don't expect this to be related to any waiting period until the server updates.

Is this a bug in DevOps or am I missing some crucial settings?