Gameplay lagging while not using GPU at all

My system has an RTX 2080 and no integrated graphics. I have a Ryzen 5 2600 as my CPU and 32GB RAM. For whatever reason, the last few times I've played the game the FPS has been at around 20. Checking task manager, the Skate. program is always at 0% utilisation for my GPU, with a high of 0.1%.