(Re)Entering VR - Lenses Stays Black

Hello guys. Sometimes after leaving vr for some reason (long flights when i’m away for a while) when getting back for landing the simulator shows on monitor it went VR mode but on the actual lenses it stays black. I can notice the Headset screen is on, but remains black. VR environment is ok, but it seems simulator is not connected to headset (head moviments not translated in camera moviment on simulator window). Anyone knows how to solve it? Or how to prevent to happen?