Because of the recent problem which made JNGP open in Reign of Chaos I used a version switcher to switch a pirated client to 1.27which wc3 patch are you on?
I don't need a fix for that, I need a fix for my tileset problem.I know this is sort of off-topic, but for your RoC problem, I recommend you take a look at this: Self-fix for JNGP on Patch 1.28
I downgraded to 1.26, still can't add tilesets from the extensions.AFAIK WEX is the only working editor with the latest patch, and WEX does not have this feature right now. I think JNGP worked in 1.26 you'll have to downgrade.
I have tried re-extracting JNGP, still doesn't work, on top of that, I noticed the custom tile pathability is also not working, when I uncheck walkable from a tile it doesn't work in game, it would still be walkable, please be patient with me, I really need JNGP to work now more than ever.That is indeed odd, while I am not 100% certain it worked in 1.26 I am pretty certain it did.
I suppose that means it is not related to the patch bur rather your computer, I suppose you have tried re-extracting JNGP?
edit: it might be a permission thing, in order to mofidy the tileset you need to have permission to modify the map. Which is not allowed in certain folders and whatnot.