Nvidia-driver-515 nvidia-smi shows "No devices were found" on PC ubuntu 20-04


I have just installed a Tesla M40 with the latest 515.48.7 driver on a fresh install of Ubuntu 20.04 desktop.

Ubuntu desktop settings (GUI) reports that the M40 is detected but the standard command-line method for detecting a device reports “No devices were found”.

Can someone suggest a workaround for detecting the device from the command-line or is a roll-back necessary?