Hi Christine,
Welcome to the Microsoft Q&A forum.
Based on your description, it is very likely that your account is still linked to your previous organization.
To leave your previous organization as a Guest user, you can follow these steps:
Step 1: Go to My Account
- If you are using a Work or School account, go to My Account and sign in.
- If you are using a Personal account or signing in with an email one-time passcode, you may need to use the My Account URL that includes the tenant name or tenant ID of the organization. For example:
[https://myaccount.microsoft.com?tenantId=contoso.onmicrosoft.com]
or
[https://myaccount.microsoft.com?tenantId=aaaabbbb-0000-cccc-1111-dddd2222eeee]
In some cases, you may need to open this URL in an InPrivate/Private browsing window.
Step 2: Leave the organization
1/ Open the Organizations page
2/ Under Other organizations you collaborate with (or Organizations if you do not have a Home organization), find the organization you want to leave, and then select Leave.

3/ When prompted for confirmation, select Leave again.
4/ you receive a message stating that you cannot leave the organization yourself, you will need to contact the organization's administrator or privacy contact and ask them to remove your Guest account from the organization.

Note: If you do not see the Leave option, it may mean that the previous organization does not allow users to leave the tenant themselves. In this case, you will need to contact the administrator of that tenant and ask them to remove your Guest account from the organization.
You can refer to the following documentation for more information:
Leave an organization - Microsoft Entra External ID | Microsoft Learn
I hope this information is helpful.
If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.
I look forward to continuing the conversation.
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