I was having this problem a week or so ago and found turning the R2 off and back on worked, though I may have also forgotten and added it back to both Field Maps and the iPad I was using.
Earlier today I was contacted by someone getting this error and it turned out the TMM app was being updated by our MDM. Once it was updated I had to agree to something when I opened the app to make sure the settings were correct. I closed it all out and opened Field Maps, connected the R2 and it all was happy again.
Don't know if any of that helps, but thought I'd put in my 2 cents.
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Lori Radunzel-Davis
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