Did I understand it right that you installed the driver manually? It’s generally better to use the Fedora Nvidia driver package (sudo dnf install akmod-nvidia), than to download from Nvidia’s website. I’m on Fedora 40 too, and currently using the 560.35.03 version of the driver on a 2080, which upgraded from 555 recently - I wonder if that’s what broke compatibility with your version of the driver. It may be that you need to update. Only thing I’m not sure of is how this will interact with manually-installed drivers…