Thank you for your post!
I understand that you blocked external access to one of your tenants due to changing the default Cross-tenant access inbound or outbound settings to Block access. Since you only blocked external access, you should be able to login using an account that is a part of your Home Azure AD tenant and wasn't invited as a guest/external user.
In order to reset your cross-tenant access settings to their defaults, you'll also need to login with a Global admin or Security admin account. For more info - Configure default settings.
I hope this helps!
If you're completely locked out and aren't able to login with any user within your tenant, due to the cross-tenant access settings, I'd recommend reaching out to our Global Customer Service team or you can contact the Azure Data Protection team for further assistance - (866-807-5850).
For future reference, I'd also recommend creating and managing an emergency access account in Azure AD. This account will help prevent being accidentally locked out of your Azure Active Directory (Azure AD) organization because you can't sign in for any reason.
If you have any other questions, please let me know. Thank you for your time and patience throughout this issue.
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