Error: SERVER_ERROR NO: 5 MSG: An account connected to site already exists

Multisite with multiple domains suddenly having an issue. Main site is working without issue. Sub site on different domain cannot be activated. Every time we attempt to activate Cleantalk on the sub site we receive the error “Error: SERVER_ERROR NO: 5 MSG: An account connected to site ******** already exists” We are never presented with the opportunity to specify the subsite key despite having the option to use a different key activated on the main site. We have tried complete deactivation on the sub site with no luck.

The page I need help with: [log in to see the link]