We have two servers running identical instances of an EE 5.2.4, using PHP 7.x via IIS. Our production machine works fine, no issues. Our backup server is the issue.
On the backup server: I can log into CP with no issues, and once logged in, I can view the site and all's well. If I'm not logged in / authenticated, I get the white screen of death. I've enabled debugging, and set $debug = 2 in index.php, so that everyone can see any errors (nothing shown), checked all debug options in CP, I've checked PHP logs, MySql logs, Event Viewer, everything I can think of. No errors are shown. Today I started commenting out template sections out of desperation, with no luck.
Clearly, something is different between the two servers. Is there anything obvious that I'm overlooking that would be bypassed when an admin is logged in, while viewing the site that would trigger for a non-authenticated user? Has anyone else dealt with this issue?