avif conversion does not work – error 0

Hello,

I am re-working my page on a fresh installation on WordPress in order to optimize it how much as possible. Currently, it’s running under a test domain. I’ve downloaded your plugin and converted all the images to the WebP format and it worked perfectly. I was amazed with the build quality of the tool and everything around it. I decided to buy the PRO version to do the AVIF conversion. Unfortunately, when I am trying to do batch conversion to the AVIF nothing happens. All I can see is errors:

21:53:51 - There was an error connecting to the API, received a response code of 0: "/usr/home/crexst/domains/crexst.usermd.net/public_html/wp-content/uploads/2023/07/Zrzut-ekranu-2023-07-29-120214-868x479.png".

The page I need help with: [log in to see the link]