Maybe it's the TE3 conflict with BoP.
No idea.
I can run a server on one PC and connect to it from another. (I have two pcs here).
I can create and play a world solo.
I've deleted and reinstalled countless times on both pcs.
I've pulled all the configs straight from the gethub just to be extra sure.
I've manually downloaded the mods in the list in case ATlauncher is giving me the wrong versions.
And still same error in all cases.
I've basically spent my day on this with no answer other then being told it has to be on my end since no one else is reporting an issue.