I was having this problem, and I sorted it out with the instructions on the following link:
https://learn.microsoft.com/en-us/office/troubleshoot/activation/another-account-already-signed-in
But I did the opposite, where it says to 'disassociate', mine was already this way, instead I change it to 'associate' saved the file and voila, I could insert another account from the same organization.
I didn't need to try option 3.
Hope this help.
Marcos Benites