Drone Connected to Remote but showing solid red light

[gregoryconely]

My school purchased 30 CoDrone Pro drones in 2018. They've worked perfectly in the past. Recently however, the drone motors won't spin, even when connected to the remote (as indicated by the multi-colored flashing light). At first, I thought it was a battery issue. So we purchased a new set of the recommended Robolink batteries and made sure they were all fully charged, yet the same problem persisted. Motors are free of all debris and obstructions and propellers spin freely when spun. Also it is not just one or a few drones. This is occurring with all of them. Any guidance would be very helpful. Thank you.

[robolink_leila]

@gregoryconely We reached out via email to set up a video call. This will be the best way to diagnose the issue. Thank you!