If you’re getting the white screen with nothing on it, that’s probably not a “can’t find a template” error: When WordPress can’t find a template, it generally falls back to the next template “up the chain,” all the way back to
index.php. If other pages display, then it’s able to find templates and would fall back for the troublesome page, which suggests to me that finding templates isn’t the problem.
For starters, I’d go through this page, and see if anything seems to match up or works: https://codex.wordpress.org/Common_WordPress_Errors
If none of those work, then I would start looking at filters and actions that Sage and Memberpress are hooking into, especially “early” ones, like
init: If you’re getting a white page, that means something is failing before WordPress can even start to generate the page, which usually means something with a filter or an action (or, possibly, something in
functions.php). Look through the code in Sage and Memberpress for any calls to
add_filter() and see if they’re conflicting.
This could also be a typo, but I notice you said that the URL you’re trying to visit is on
domain.test but the directory you’re looking for logs in is
domain.com. You would need to look in
/srv/www/domain.test/logs/ for log files on
domain.test if you’ve provisioned your server with Trellis normally.