How to fix nginx error when opening wp-admin on a WordPress site?

Question

PHP

There is a site on WordPress, everything worked fine until the installation of the W3 Total Cache plugin, perhaps it was after installing it that I couldn’t access the admin page, it says:

I didn’t see anything useful in the logs ... What could be the problem, and why it only appears to the wp-admin page?

Answer 1

And this is not an nginx bug.
This is a 503 error. Look in the php logs (php-fpm/php-cgi what do you use there).