A group wants to move under the cover of spirit invis and presumably spirit movement. The area they are moving into (through, under) has six drones with visual and motion sensors. Does spirit service invisibility protect them from the drones? Thanks, I couldn't find this ruling under drone vehicle sensors.

Spirits don't give invisibility (well, short of having the innate spell power) they give concealment. Which is a -force modifier to perception tests. Assuming the drones are rolling sensor+pilot for their perception tests, yes, it should apply.

Note that there are a ton of alternate interpretations and houserules covering various aspects of spirit concealment though.

Its a physical power, so yes, it affects the drones sensors.