Hi @nick98!
I looked into it and tested importing the script on code snippets 3.9.6. I downloaded the script, opened the zip file and uploaded the .json file. From there it read and could import the .php script.
Maybe you could have a look into which plugin version you are using and maybe update?
If you are using the latest plugin, try to disable other plugins and try again, as this might be a plugin compatibility issue.
