[FIXED] WordPress admin sends empty response but frontend works

Issue

All my WordPress installs suddenly have wp-admin inaccessible after installing. I've repeated the procedure several times, and in different locations to avoid caching issues.

Steps:

1. download WP from the official site
2. do a fresh install in an empty database
3. log in to /wp-admin

After logging in I get an ERR_EMPTY_RESPONSE and in the console I see the error "crbug/1173575, non-JS module files deprecated." After this the admin section is completely inaccessible.

The site itself however works fine and I see the default Hello World post.

My existing WP install run fine, but any new ones I make behave as described.

I have tried rebooting and restarting Apache.

I am on MacOS, PHP 7.3.29.

Solution

This isn't exactly a solution, but doesn't look like anyone will be able to answer, so I'll provide the info I can in case this happens to someone else.

The problem happens when previously logged in and wp-admin is trying to "reauthorize" (the parameter "reauth" is present in the URL).

The issue seems to have to do with serving WordPress over MacOS's own Apache installation, but works fine when serving over a Mampstack installation. (I had previously gone over to the MacOS built-in installation because I needed MySQL and not MariaDB, I guess I'll have to run them in parallel.)

Answered By - Simon