Hello @Bergs ,
Thank you for contacting Microsoft QnA platform. When trying to access Microsoft Azure Portal by default you would be authenticated against all the tenants you are part of. As you are able to access Azure Portal when using tenant/org identifier [https://portal.azure.com/organization's domain] it means you are blocked on specified directory. You find all the orgnizations you have access to by visiting switch directory option on Azure Portal under profile.
I would request you to please re-evaluate the access you have on all organizations. If you no longer need access to organization on which you are blocked you can try to leave the organization using steps mentioned on following article: Leave an organization: https://learn.microsoft.com/en-us/entra/external-id/leave-the-organization
Once you leave the organization you are being blocked on you would not longer need to use Org Identifier on Azure Portal URL and you should be able to access it without any issues.
I hope the information provided above helps you resolve the issue. Please "Accept the answer" if the information helped you. This will help us and others in the community as well.