I had similiar problems. Another odd factor was that the script would work in the global python environment on the Windows machine but not in a venv. The resolution ended up being: 1/ Delete the venv (might be enough to uninstall certifi, boto3, botocore, urilib3) 2/ Install certifi first. 3/ Then install boto3 etc.

Another issue I have seen on Windows is if the venv is on a network drive instead of local drive.

Does your issue fall in either of the above?