Additional features, settings, or issues not covered by specific Microsoft Teams categories
Hi MMD_1872
Thanks for your post in the community.
From your description, my understanding is that you use your two accounts to sign up for Teams free but get error message. If I have any misunderstanding on it, please feel free to let us know. According to Error Code, I suggest you can clear the cache of browser to sign up or use InPrivate mode in the browser to check if it is workable as the cache could lead to the mistake on identifying credential information. Besides, maybe the network environment associated to the issue. Therefore, kindly choose the stable network environment to check the result.
If you have anything unclear, please feel free to let us know.
Regards,
Joey