Can you please try the same portal in the Incognito mode if you are using Chrome and Inprivate if you are using Edge Browser?
Also have a read through this article for switch of Azure AD and some process around it. change-azure-ad-connection
There is a known article and steps to try the switch process using the tenant ID - unable-to-switch-directories-in-azure-ad-616d16ced5e1
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