My 6 series is constantly doing this same thing. Completely nonresponsive swiping up or down to get control center or notifications. But for some reason you can press and hold to change watch faces and swipe left to right. It randomly happens and then randomly starts working again. The last couple times it’s happened I have pressed the side button to bring up the app switcher and closed out all the apps. Each time I’ve done that the swipe up and down miraculously comes back. It must be an app running in the background that’s causing the glitch.Sometimes I can swipe up or down for notification or control center, but sometimes I can't with the Series 6. It feels like a software issue. When the watch display is on the always-on display mode, it has no problem with the swipes.
Even after I restarted the watch, it happens again sometimes. Does anyone else with the Apple Watch Series 6 have this issue too?