I think this is a bug that happens sometimes when updating an email message from the previous version.
The issue is that the new version creates the email file at /webassist/email/ and not the WA_Universal email folder any more, but the path isn't updated in the code properly.
include("WA_Universal_Email/WAUE_confirm_1.php");
should probably be:
include("webassist/email/WAUE_confirm_1.php");