Troubleshooting application registration
If you choose the Automatic registration option when configuring a source Office 365 connection in the program, the connection wizard attempts to register CodeTwo Exchange Migration in your Azure Active Directory. If the attempt fails in the Configuration step (Fig. 1.), click Details to learn more about the reason for the failure.
The most common error messages related to application registration are listed below. Study them and learn about possible solutions.
This error usually occurs if the account provided in the Application registration step of the connection wizard doesn't have enough permissions to perform the registration. You need to close the connection wizard, open a new one, and this time use the account that is a global admin in the Office 365 tenant that you intend to connect to.
Keep in mind that even though the program failed to register itself, it has created the CodeTwo Exchange Migration Source entry in your Azure AD. However, this application is missing the necessary permissions that only an Office 365 global admin can grant. You can delete this application by following these steps or grant the necessary admin consent in the Azure Active Directory admin center and then configure server connection by following the manual registration path.
Try also updating the program to newest version, which you can find here.