Email Template Editor | Not loading, no edit interface

WP 6.9.4
FluentCRM & Pro 3.1.8
Host Rocket.net

I'm getting nothing to edit with. This happens on the live and staging sites.
The preview works though.

How it looks

How the HTML structure looks (I wouldn't know if it's correct, just adding it in case someone else does.)

Console Error:

Uncaught (in promise) Error: A listener indicated an asynchronous response by returning true, but the message channel closed before a response was received