Dear Jessica Neo
Thanks for choosing Microsoft Community.
Based on your description, I know the scenario you met.
It sounds like you changed the email associated with your Microsoft account, but the change has not been reflected in the Microsoft Teams organization where you are a guest. This can happen if the organization has not updated their guest user list to reflect the change in your email name.
To resolve this issue, you can reach out to the organization's IT administrator and request that they update their guest user list to reflect your new email name. Once they have done so, you should be able to access the documents and meetings in the organization as before.
Hope this can help. If there is any update or you have any other consult, please feel free to let me know. I will continue to help you based on the information you provide. Your understanding and co-operation are highly appreciated.
Thanks for your precious time. Have a nice day.
Sincerely
Katherine