Hello aml7785,
As far as I understand, after migration to Adobe Admin Console, it is not possible any more to use individual API keys for non admin users.
If you are using the general API key from Setup > System > Customer Info, I would try to reset / regenerate the key.
Apart from that, I would suggest adding a Web application under Setup > System > OAuth2 Applications, as it is much more secure and flexible.
Writing the whole authentication process in Python was really challenging to me a couple of months ago, but the result is working like a charm almost every day, and I am also a bit proud of it.
Do not hesitate to ask, if you need help with that.
Regards
Lars