Error occured during creating the thumbnail

Hi,
I'm receiving "An error occured during creating the thumbnail." in the Publisher theme. I have read this forum for the solution, but none of found worked for me.
Permissions of cache folder are set to 755, I have made also modification of few files (and restored them later on).

Can you, please advise how to sort this issue out?

Hi,
Unfortunately, the Publisher theme is not supported anymore. Try to use 3rd party plugin (News Show Pro) instead of the widget included in theme files.
https://github.com/GavickPro/GK-News-Show-Pro