Global or privileged role admin prerequisite
You must be a global or privileged role admin to consent to the Microsoft 365 permission sets.
If you don't have that access level, you will need a global or privileged role admin to consent on your behalf.
To learn how they can consent, see How a global or privileged role admin can consent to ShareGate's Microsoft 365 permission sets
Verify that the associated Enterprise application is installed and reinstall it
Follow the guide to revoke consent to a permission set, and if you find the enterprise application at step (3), delete it.
Then, retry consenting to the Microsoft 365 permissions with your global or privileged role admin account
ShareGate Migrate
If the permission set was consented to and the change is not reflected in ShareGate Migrate, try reconnecting your tenant in Explore.
If the reconnection does not work and you connect with Browser authentication, you can try turning Single Sign-On (SSO) off, as it can prevent ShareGate Migrate from confirming consent was granted in some cases.
Contact our technical support team if you experience further problems with consent to ShareGate's Microsoft 365 permission sets.