Frozen apple watch
My watch (series 7) appears to be frozen. I had it on the charger for a few hours so it should be fully charged, but nothing works. I've tried resetting it, but the slider won't appear when I press the buttons on the side, so I can't turn it off. The only things that show up when I hold the buttons is the time in the upper right corner and a red lightning in the upper left corner (it turns green when I place it on my charger again.) Where do I go from here? I've looked through the topics here, but nothing they suggest works. I'm stumped.
Apple Watch Series 7, watchOS 9