It seems that you had changed the email address for your Adobe account.
This generally happens when you use an email address which is already registered for another Adobe Sign account. So when you had changed the email address for the Adobe account, it got changed for the Adobe Acrobat. However, as there was already an Adobe Sign account under that email address, it was not updated for the current account linked with Acrobat.
In this case, you will need to first free your new email address from the other Adobe Sign account. Then you will be used that email address for the Adobe Sign account linked to Acrobat.