so i downloaded the new version of the mod (with the new version of nuclear throne) and when i clicked coop it wouldn't let me invite my friend (they had the same version of the mod and game as me) to the game. it put me into a game lobby immediately and i could not invite people.

Are you sure that you are running NuclearThroneTogether.exe and not the original NuclearThrone.exe? The patcher says about this.

yea i was stupid but i found out and started the together.exe and it worked