Can’t save settings

Hello, Hannes.

I am trying to modify the email template – nothing special, just changing header/footer colors etc. But I can’t save anything. After moving to the next tab I see that all my changes go back to the original teal color.

Where can I look inside to check why it is not saving the modifications?

I currently use Comet Cache and I am on Cloudflare, however it may not have anything to do with WP HTML Mail – I have just tested on another website in the same virtual machine on the same Apache instance and everything worked fine.

Where can the problem be? I did not try to re-install. All files of the plugin belong to www-data.

Thanks in advance