Thank you for reaching us!
Based on the error message, guest user access is restricted in the External collaboration settings, or you are using a free version of Entra ID.
The free version of Microsoft Entra ID comes bundled with subscriptions to commercial online services like Azure, Dynamics 365, Intune, Power Platform, among others.
Therefore, you may opt for one of the above-mentioned subscriptions, or you may require P1 or P2.
subscription: https://www.microsoft.com/en-us/security/business/identity-access/microsoft-entra-id#:%7E:text=The%20free%20edition%20of%20Microsoft,%2C%20Power%20Platform%2C%20and%20others.
For more information, please refer to the below post which is similar to your issue.
https://learn.microsoft.com/en-us/answers/questions/1352059/azure-portal-keeps-throwing-aadsts16000-errors
I hope this information is helpful. Please let us know if you have any further queries.
Thanks,
Akhilesh.
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