I've used Trello daily for years and years. Never had a problem. Today, I opened the app to get a link off my main business board and something had eaten ALL my cards. I could see all the normal list headings, but every single card was MISSING. I went on desktop and the board looked perfectly fine, but I immediately made a copy of it just in case. Of course, this is my MOST valuable and difficult to replace board. I was able to see the copied board just fine in the app then, but the original board is still just a skeleton board on the app.
I'm on the free plan - iPhone 12 and a Windows 11 laptop. Note that I did just upgrade my phone to IOS 26.2 and this *might* be the first time I've opened the app under the new system, but I checked a couple of other boards and they seemed just fine. I also closed and restarted the app - no help there. I did put a brand new card on the board as a test - that one did show up...
Mysterious!