To log in as an instructor or user, you'll need to verify your email first: Verify First.
The reason for this requirement is that the option to disable email verification in the admin panel's settings hasn't been enabled. Please refer to the attached screenshot for instructions on how to disable email verification: Disable Email Verification.
After you disable the verification, the admin will no longer need to verify users' or instructors' emails. They will be able to log in to their accounts directly.