i faced the same problem with my b550 aorus elite + rtx 3070 aorus master v1.1
Ive found out why reinstalling nvidia driver and fusion doesnt work, in my case.
So, just follow what the above had mentioned, before restart, uninstall nvidia driver (just the driver will do) and uninstall rgb fusion (i did uninstall aorus engine as well).
Then, SHUT DOWN ur pc instead of restart, switch off the plug to cut the power off completely. Turn ON ur pc after around 10 second of power off rest.
If ure using a aorus gpu with led display, u should now see the led display is resetted and showing the chibi. (from what ive found, ur gpu is reset only if chibi shows up during restart and this was only successfully reset when i shut down and power off my pc instead of RESTARTING)
Finally, u can now install ur rgb fusion 1ST (in my case i installed aorus engine 1st but i install my rgb fusion from aorus app centre),
congratz u will see ur gpu get detected in the rgb fusion, only then install ur nvidia driver from the existing nvidia geforce experience software.