Two things that, no matter how many times I run into them, I end up spending time figuring out what they are before slapping my forehead.

Teams Adaptive Card Version

The current supported version for Teams Adaptive Cards is 1.5; anything else will fail. In the Adaptive Card Designer, you are allowed to go higher, but when you go to use in your app, it will fail.

Plugin Registration Tool Updates

Sadly, I don’t have a screenshot, but there have been a few times where my plugin registration tool to a PowerApps tenant starts to fail. From day to day, I have no idea why; it just does, with no error to help you move forward.

The issue is that your PRT is out of date, the solution is a quick update via

pac tool prt --update 

Shown below for the CMT tool

This might seem like a silly post, but these kinds of things, even AI doesn’t know how to diagnose them, because the errors are so far-fetched from the actual issue that it sends you down a completely wrong path.

The solution is always, always, always, better error handling.