I can't find anything on this so far. My Vive Pro has been rock solid, and then starting last night, having this issue;
Start SteamVR, and it says the headset is tracking and looks ok, drivers up to date.
Lenses are black, but then flash white 3 times, and go black again. I tried re-plugging in cables, different video port on video card, rebooted windows, restart Steam, hitting the button on the left side of the HMD - no change.
However, if I let the headset sit, it does go into standby mode. If I leave it alone for a few minutes, suddenly the headset just turns on, stops flashing, and work