I am getting an error when I try to sync on Mac. The problem seemed to come out of nowhere. I updated to the most recent version of Anki, from 2.1.38 to 2.1.39, without any improvement. It seems similar to others who have posted recently, but the error message is slightly different:
A network error occurred.
Error details: error decoding response body: missing field
modelsat line 1 column 17