Hi,
looking at the source of that page, there doesn’t appear to be any plugin related html output at all, not even an error message. This is very unusual, plugin would normally say something at least. This may indicate it is not getting run at all.
right after the paragraph to ‘search for members’ there is some custom styles for “.user_search_results” That is not a class that this plugin uses but would appear to relate to the page.
1.Are you sure you using this plugin?
2. If yes, Is the shortcode actually still in the page? (sorry to ask but sometimes one finds it’s these sorts of things!)
3. IF yes, Is the list still working in admin area?
4. any errors or strange things in the cache log page
5. Have you added or updated any other plugin or theme since you last saw the userlist?
One possibility is that something is stripping the shortcodes, so list not even running in front end, or there is a clash. Temporarily deactivate all other plugins as per https://webdesign.anmari.com/2932/debugging-a-possible-clash-between-plugins-andor-a-theme/
This would also help detect if it’s running out of memory, as deactivating other plugins would reduce memory load. You could also check the system log, but usually it’s easier to quickly put site into maintenance mode, deactivate, refresh page and see what happens.
Let me know how you go