You have the “Trusted IP” feature enabled, which means that you can only use the account with the IP address (address list) you have specified.
In all probability, it is likely that the IP address from which you logged in is not a “Trusted IP” and is Dynamic. Before enabling the “Trusted IP” function, it is recommended that you make sure you use a Static (permanent) address to connect to the Internet.
To solve the problem, please log into your account from your “Trusted IP”. If you are unable to or your “Trusted IP” turned out to be Dynamic (you can also check this with your Internet Service Provider), please contact the EXMO Support from the email address used during EXMO account registration. Please send an email to firstname.lastname@example.org specifying the reason for your request.