Thanks for reaching out with the issue. I had a few questions for you, these will help us expedite our investigation -
When you say, they no longer work, what is the behavior you see? Is the app opening, but the images aren't loaded ? Are you on the latest PowerApps Version? If not, can you please try to get the latest and reproduce the issue. Can you please share a session Id ?
To look up session Id ,you would have to -
1. Close (kill PowerApps) and reopen powerapps on the mobile device
2. Sign in, if reuiqred
3. Click on the hamburger menu , on the left top corner of the app
4. Click on 'Session details' menu item.
5. Note down the session Id from the popup and close the dialog