This was resolved by long-holding power button on VU and resarting. Before filing this bug: I tried toggling cvox2, reconnecting cables, restart Samus, and suspending/resuming VU. 

Looks like this is working again? Re-open if not. Note that there is a known issue thta you need to press a hardware key before output shows up.

I finally figured the minimal repro to make this happen:
1. Given Active Braille display state, where VarioUltra is in USB Braille display mode connected to Samus with ChromeVox NExt via USB cable;
2. Close lid of Samus > Disconnect USB cable
3. Open lid of Samus > sign-in > connect VarioUltra to Samus via USB cable

Observed: No Braille, even pressing Braille-input keys, navistick, display keys, and system keys
Expected: CrOs content to be in Braille

Note: This is where it's required to reboot VU40 to get Braille back, which takes ~30 seconds.

Please re-open per #5

Correcting title.

Do you get braille before signing in?

Yes, I get Braille on CrOs sign-in screen