It sounds like the only thing you did was signaling, not STUN and TURN.

If you do both STUN and TURN it works on most networks. I've worked at really restricted work sites, and while STUN fails at those if you have a TURN server then it almost always works.

These sort of comments are why people think webRTC is unstable while the same people use slack calls which literally use webRTC.

I might be wrong, but please don't talk about network reliability in webRTC without specifying if you have a working STUN and/or TURN setup.