The kernel driver is missing. How did you initially install the driver? Please check if you booted the correct (latest) kernel in grub menu. Please also post the output of
dkms status
ii libnvidia-cfg1-470:amd64 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA binary OpenGL/GLX configuration library
ii libnvidia-common-470 470.86-0ubuntu0.20.04.2 all Shared files used by the NVIDIA libraries
ii libnvidia-compute-470:amd64 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA libcompute package
ii libnvidia-compute-470:i386 470.63.01-0ubuntu0.20.04.2 i386 NVIDIA libcompute package
ii libnvidia-decode-470:amd64 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA Video Decoding runtime libraries
ii libnvidia-decode-470:i386 470.63.01-0ubuntu0.20.04.2 i386 NVIDIA Video Decoding runtime libraries
ii libnvidia-encode-470:amd64 470.63.01-0ubuntu0.20.04.2 amd64 NVENC Video Encoding runtime library
ii libnvidia-encode-470:i386 470.63.01-0ubuntu0.20.04.2 i386 NVENC Video Encoding runtime library
ii libnvidia-extra-470:amd64 470.63.01-0ubuntu0.20.04.2 amd64 Extra libraries for the NVIDIA driver
ii libnvidia-fbc1-470:amd64 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA OpenGL-based Framebuffer Capture runtime library
ii libnvidia-fbc1-470:i386 470.63.01-0ubuntu0.20.04.2 i386 NVIDIA OpenGL-based Framebuffer Capture runtime library
ii libnvidia-gl-470:amd64 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA OpenGL/GLX/EGL/GLES GLVND libraries and Vulkan ICD
ii libnvidia-gl-470:i386 470.63.01-0ubuntu0.20.04.2 i386 NVIDIA OpenGL/GLX/EGL/GLES GLVND libraries and Vulkan ICD
ii libnvidia-ifr1-470:amd64 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA OpenGL-based Inband Frame Readback runtime library
ii libnvidia-ifr1-470:i386 470.63.01-0ubuntu0.20.04.2 i386 NVIDIA OpenGL-based Inband Frame Readback runtime library
ii linux-modules-nvidia-470-5.11.0-37-generic 5.11.0-37.41~20.04.2 amd64 Linux kernel nvidia modules for version 5.11.0-37
ii linux-modules-nvidia-470-generic-hwe-20.04 5.11.0-37.41~20.04.2 amd64 Extra drivers for nvidia-470 for the generic-hwe-20.04 flavour
ii linux-objects-nvidia-470-5.11.0-37-generic 5.11.0-37.41~20.04.2 amd64 Linux kernel nvidia modules for version 5.11.0-37 (objects)
ii linux-signatures-nvidia-5.11.0-37-generic 5.11.0-37.41~20.04.2 amd64 Linux kernel signatures for nvidia modules for version 5.11.0-37-generic
ii nvidia-compute-utils-470 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA compute utilities
ii nvidia-driver-470 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA driver metapackage
ii nvidia-kernel-common-470 470.63.01-0ubuntu0.20.04.2 amd64 Shared files used with the kernel module
ii nvidia-kernel-source-470 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA kernel source package
ii nvidia-modprobe 470.57.02-0ubuntu1 amd64 Load the NVIDIA kernel driver and create device files
ii nvidia-prime 0.8.16~0.20.04.1 all Tools to enable NVIDIA’s Prime
ii nvidia-settings 470.57.02-0ubuntu1 amd64 Tool for configuring the NVIDIA graphics driver
ii nvidia-utils-470 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA driver support binaries
ii screen-resolution-extra 0.18build1 all Extension for the nvidia-settings control panel
ii xserver-xorg-video-nvidia-470 470.63.01-0ubuntu0.20.04.2 amd64 NVIDIA binary Xorg driver