If you encounter an error like the one above that states that
"Sorry, the account is already in use by another User, Contact us if you think this is a mistake"
What this means is that the account was already added to another Gramto account. You cannot attach a single Instagram account to multiple Gramto accounts because this places the account at risk of running activities simultaneously on both accounts.
To resolve this issue;
1. Login to your previous Gramto account and delete the Instagram account before adding to the new account