How do I set sender domain?

Hello,

I hope all is well.

I am encountering issues with setting my sender domain for adding my corporate domain to the bulk email settings page. For some reason it is saying that the domain exists in another sub account. I did not do this setup before in this Creatio instance, so I am unsure why I am getting this issue. 

Any help would be greatly appreciated. I attached an image of the error for your reference.

If the error message is not visible from the image, I am pasting it here:

 There was an error while adding domain: Unable to set sender domain: [Domain]. Message: This domain is associated with another Sub-Account (" [Sub Account ID] ") and cannot be added to this Sub-Account. If you need this domain to be associated with more than one Sub-Account you need to remove it from the Sub-Account and add it to the main Account. Main Account domains are always available to all Sub-Accounts.