I need some help with my entities

Hello!
Can someone help me with a problem that I have making entities? I am trying to make a TNT mod that adds a bunch of tnts to the game but the primed TNT entity is invisible. I have tried to fix it in many ways. This is not the only time this has happened to me. I tried to make a mod with an entity that was unkillable, but it did not exist. Not the texture or the entity. Reply if you know how to fix this. Thank you! :-)