ssssp I downloaded and checked the attached .zip file, and indeed, opening the .spine project and importing the .json file did not work. I looked at the spine.log file and found the following log, so I edited the .json file directly to remove the clipping attachment and was able to open it.
java.lang.IllegalArgumentException: No enum constant lk.clipping

Here is the Spine project that you can now open:

I am not sure what the clipping attachment originally did, but I think I have restored most of it with it, so check it out.

ssssp Check the spine.log file stored in your user folder after importing. The location of the spine.log file depends on your operating system, so please refer to the following page: https://esotericsoftware.com/spine-troubleshooting#spine.log

Hmm, I will check the attached project, but please understand that if there are a large number of other similar projects, we will not be able to check them all.

ssssp I am glad to hear that the problem has been resolved!