Sorry this reply is so late, the problem your having does seem to be a strange one.
Firstly lets check off the basic questions like do you have the required files installed ?
(this includes the IDE Antlr 2.7)
Have you made sure to make sure your material is a direct x shader that uses the correct game path ?
Included an OBBox ? (basically a square that is for hit detection)
Made sure your hierarchy was correctly orientated and each pivot set correct ? (though you'd probably not be getting that error.)
Suggestions to try : make sure your using the correct version of max , slightly different versions exist for that year it is strange though so just note however a few versions with this exporter.
tank tutorial with special thanks to X3N and I added some commentary (Note this tutorial worked well for me and I was / am able to add models of my own but I find gamers of this game to be unthankful with many fellow modders of this platform being quite nasty people.
Part 1
Part 2
Part 3
Feel free to reply however I rarely visit modding forums these days so don't be surprised if I don't reply.
Questions asked in the youtube channels may also be ignored as I don't intend to be the goto man for a community that was in the most part absurd. Note the pirate mod is no longer in production.(though one day I might just finish it for myself )