I'm applying joint forces/torques or setting velocities -- why aren't my Joint objects moving?

Even if you're setting joint velocities or forces/torques, the joint may not move if the strength limit has not been set high enough.

Make sure you've called the joint method set-strength-limit with a high enough limit, otherwise the joints won't be able to move. Depending on the mass of the connected objects and other factors, the default strength limits may be too weak to get the joint to move.