I think it doesn't work on servers because of the way 1.12.2 handles initializing mod animations and I never could find a (consistently bug-free) way to make animations and servers work simultaneously. I was planning on updating my mod to check if it's being run on a server and if so, disable animations but I haven't really had the time to implement that yet. I might do that soon but it just depends (on if my profs. want to be hardasses about assigning homework this semester or not)
I know of at least one person that found a workaround though but I can't remember what he did. I think it will work just out of the box if you run a lan server using the Minecraft launcher itself. That can still be pretty fun and the TNTs will be available and explode correctly for all players on the lan as long as they all have the mod installed.
When I port this mod to 1.13, I'll try to push to find a hack/workaround/correct way for it to be run in a server without crashing it and if possible, update the 1.12 version as well.