First thing I’d be trying would be to switch the another theme temporarily to see if it is the theme that is causing the issue. Obviously make sure you have a way of backup/restore before switching. If that solves it (or perhaps is not conclusive) then write it your functions.php to work around it. That, or contact the theme provider and see if they can give you steps for a workaround.
Hello. As I said, I tried with and without “USE HTML for Emails”.
Anyway I found the cause of the problem. The website theme had a (core.html.php) file modifying the Email Content Type. Added function in functions.php which removes the function hooked in core.html.php and another filter which which we have added which changes the ContentType to Html, with an exception created for other plugins.
