D7 Custom image styles not uploading


I’ve been struggling for a while with a problem that if I upload an image to my site, the original image uploads correctly, default styles like “thumbnail” as well, but my custom created styles do not work.

Custom styles worked on my site for years but suddenly this problem appeared. I have 2 environments – for development/testing and production. This problem appeared on both environments and not after any updates or new modules installed as far as I know.

I tried to create new styles and it does not work either – the directory gets created but is empty and no files are saved there.

There are no messages in Drupal logs or apache logs. Permissions checked and correct. I wasn’t successful with locating the reason of this problem.

Any suggestions?

Thank you for your answers.

If you need any more information, just ask and I will do my best to give it to you.

Drupal version: 

Source: https://www.drupal.org/taxonomy/term/22/feed