Hey,
I just had the exact issue. After installing Power BI and all the drivers onto a new computer, it stopped working.
After a lot of time, I managed to find the issue. In my case, I downloaded the 32-bit version of Power BI, and the driver supplied on the MongoDB website (Download Atlas SQL ODBC Driver | MongoDB) is a 64-bit one.
So in my case removing the 32bit Power BI version and installing a 64bit version solved the issue.
I hope it will help someone else in the future.