Only the owner of this account can update the email address.
You are trying to change your WePay account email address and receive the following error...
"Only the owner of this account can update the email address."
This means that you already have an existing WePay account associated with this email address.
If you wish to use an email address that is attached to an existing WePay account that you no longer use, we can ask WePay to simply delete the existing/old WePay account which will thereby remove that email address from their system, enabling it to be used for a new WePay account.
However, if you want to keep the existing WePay account active and separate from the DoJiggy Payments account, then you would need to just use an alternate email address for the new account.