The first thing to check would be your server logs. Something’s probably throwing an error, and that’s where it’s likely to be recorded. You might also look at Sage’s own sage.log.
I’d installed a new WP from scratch along with my custom Sage 10 Theme (production server and local), and then trying to install new plugins (akismet, Classic Editor) but it keeps giving an error (Installation failed: ) and sometimes disables this page /wp-admin/plugin-install.php.
The server error logs only throws this:
[21-Apr-2021 15:34:30 UTC] PHP Warning: set_time_limit() has been disabled for security reasons in /usr/home/rebiketaller.com/web/rebikewp/wp-admin/includes/class-wp-upgrader.php on line 471
I commented this line in 471 in class-wp-upgrader.php and it worked, plugins are installing correctly.
As we all know it is not the best choice to modify WP core files. But it is the only way I found to fix the issue.
I wonder if Sage 10 Theme is causing this situation. Im not having this issue with legacy WP themes active.
I have a playground/test WP installation if you want to check it by yourself. I bring back core files to original with uncommented set_time_limit() line.
In the latest Sage 10, you’ll find acorn.log inside theme/storage/logs.
I don’t believe Sage can cause such warning, however, this version of sage doesn’t seem to tolerate warnings and it breaks the website when there’s one. Previous versions were ignoring warnings.
I’d recommend contacting the hosting company about enabling set_time_limit() which should resolve your issue without modifying core WordPress files.