i made a flame thrower in blockbench and it wont work

so i made a 3d model of a flamethrower in blockbench then ported it to mcreator making sure it had been exported to the right version and textures worked. it did not work and is the default purple and black cube. i have been able to make a 3d modelled shotgun before and it worked so i keep getting frustrated. i tried other forums and non of there answers worked.