Converted images are with 0 size and it doesn't create higher resolution version

Hi Marcin,
I'm sorry for this inconvenience, please go to the advanced tab of the plugin and enable the debug mode, the remove the optimized images directory, its name is jrio_cache and reload any page with images, this will generate a log file below the administrator/logs folder.
please send this file to admin@joomreem.com and I will analyze it to find out and fix your problem.

Best regards

I've generated logs and sent them to you.

Thanks!
Would you please let me know what is the memory limit of your site?
You can find it at: System > System Information > PHP Information tab, the look for the value of memory_limit.

You will find two values: Local and Master, the Local value is what I'm looking for.

Best regards

memory_limit 16020M

16GB, so it should be more than enough.