While it may not necessarily be helpful, I didn't see it listed in your troubleshooting. Have you tried updating or reinstalling your video card drivers (possibly rolling back a minor revision or two, for stability. It's been known to be needed occasionally)? I know, Daz rarely gives useful advice ...
First ... tell everyone what versions of Operating System, Daz and Octane Plugin you are using. Is the plugin licensed? Did you adjust any preferences for the plugin?
Lastly... just load a basic character and see if it renders. i.e. Stock Genesis 1
OcDs stopped rendering last night. The full error is: "3 render engine failures within a minute - giving up! (Critical) You should now save your work and restart DAZ Studio! If this error persists the GPU driver may have crashed!" This message appears after restarting Daz and after reboot as well ...