We were going to start sending email campaigns in production and discovered that in EXM if we go into a message tab the Preview does not work. It just shows
An internal error has occurred. This is happening with our custom base email template, as well as the out of the box sample newsletter.
Sitecore 9.1.1, SXA 1.8.1.
There is nothing obvious as to what the internal error is in the log files or in application insights. I also tried using fiddler but the response of the failed request just has the same message as appears in the body field below.
All other environments are fine - it's just production. I have checked all the things published (templates, renderings, email root).
If you click into the body the
Experience Editor loads fine with the modules all ok. Saving and closing just leave it in an error state on this screen and in the Content editor preview tab.
Have discovered that accessing this CSS file is erroring:
Although still unsure why this file is not accessible via web browser.