I am getting the same error. It started happening after I created a template from my list and created a list for testing. The original list started throwing the error. I've since deleted the duplicated list and the template files and removed them from my recycle bin.
I've gone to edit the PowerApps form and tried the following, but Ihave not found a resolution:
1. Deleted and re-added the data source
2. Deleted and re-added the connection - this was a huge hassle because I had to go and reconnect all my flows!
a.re-added the data source after recreating the connection
It has been 24 hours, my final hope was that SharePoint just needed to process things, but it is still not working this morning.