UPDATE:
In case it helps anyone, it was because Frame Generation was enabled. For some reason, Vsync is greyed out when Frame Gen is enabled. I think I’ve seen that on another game as well.
I’m pretty sure I had vsync enabled in the beta and server slam but it’s now greyed out.
I’ve tried Window Full Screen and Window.
I guess I could force it in my Nvidia driver but it would be nice if I could just enable in game.
Any ideas?