As an addidtional security measure, authentication is required for Coins account log ins done on a newly detected device. Please note that you should click the email verification using the new device where you are trying to log in.
Once "Approve device" is clicked on the email verification, you may proceed to your Coins app to press I've clicked the confirmation link button.
Attempting to log in using your mobile device and clicking the verification email using a desktop/laptop or another device can cause your login failure.