Wordpress wp-admin suddenly lost its style

Question

I'm really baffled about this. In the last couple of days (since I was using the site last), my Wordpress install has suddenly lost almost all of its formatting (only the top bar seems to work.

The CSS does seem to be loading, but its missing tons of them:

Here is the same page on another site (same version of WordPress);

I'm at a loss as to what could be causing this all of a sudden. The front end if fine, just to reiterate that.

UPDATE: thanks to someone over at https://wordpress.stackexchange.com/, I followed these instructions:

Try the following: 1) Clear your browser cache. 2) Re-install WordPress (keep wp-content and your database, just reinstall the core files)

....and that has now fixed it :) Thanks to everyone who offered suggestions though!

Answer 1

Another solution, try adding this to wp-config.php:

define( 'CONCATENATE_SCRIPTS', false );

Answer 2

I solved this by re-registering dashicons. I disabled it fully with:

wp_deregister_style( 'dashicons' );

After I commented out this line it worked normally. Hope this helps.