Let me quickly bring you up to speed on my issue..
I'm using Gamemaker Studio 2. I've been using v2.1.5 from mid-2018 due to a bug that affected my project. Until recently it was fixed in v2.2.4 and I upgraded. All this while, I have been using an extension that allowed skeleton animations made from Spriter to work inside Gamemaker (extension made by Nux). But after the upgrade to v2.2.4, the extension broke. I contacted the author and he told me he won't be working on it anymore (at least for a long while).
I rolled back to v2.1.5.
Bought Spine (v3.8.75).
Painstakingly rerigged + reanimated everything from Spriter into Spine.
Exported the data and it does not work in Gamemaker..
I asked the Gamemaker Forums community on the stable version that worked in v2.1.5 and it was Spine v3.4.02..
Downgraded Spine to v3.4.02 but I can't open my Spine project anymore..
Please tell I don't have to rerig + reanimate everything again now in Spine v3.4.02, please... Any help? 😢
UPDATE
I've tried the JsonRollback tool as mentioned here: http://esotericsoftware.com/forum/Open-project-in-an-older-version-11458. I was given only two options to rollback to 2.1 or 3.7 and I went with 2.1. Downgraded Spine to v2.1.27. Imported the data but it doesn't open.
UPDATE2
Solved.