You must set it to: "Video in motion","Yes (All speeds) - Recommended" and after config you need to close and lock car for at least 5-min, because car need to completely reboot. After this it will work.

We have not experienced such behavior. The "Video In Motion" feature worked in all instances we configured.

My suspect it that the car was not (if ever) upgraded by Volvo. Go to a dealer and ask for ICM/IHU upgrade (Software P/N 31268488)
or Total MOST upgrade P/N 31357702, whichever will be cheaper there.

The Video in Motion (as loaded by VDASH) may get erased, if so, restore it in VDASH (at no cost).