I had this issue, and when it finally ended up working it ended up being me pressing the HDMI further into the port. I guess it was just a smidgen loose. Dunno if that'll help you though.
The connection in the headset, linkbox or PC? I haven't unplugged the cables from the headset completely yet. I'll try that tonight. All other cables have been reseated and swapped out.
Oh yeah, forgot to mention that I did get it working a week ago by uninstalling SteamVR and the USB drivers and rebooting a bunch of times. The headset finally had a green light and it worked. As soon as I rebooted my PC and tried to play the next day, error 208 happened again and I haven't been able to repeat the fix doing the same steps. I even removed all Oculus Rift software just in case it was causing issues somehow.