I find my self every other time I change the lens set up on my camera my Ronin S deactivates it self. I have to connect it to the PC or update/downgrade the firmware in order for it to work again.
Are you turning your camera OFF, before lens changes and is it still connected via USB to the Ronin? When the camera is connected, the gimbal is communicating with it and it’s possible that is doing something weird, but I’ve never heard of it just “deactivating”. I did have a problem with a smallHD monitor doing something similar(requesting registration continuously even after being registered), but it did it right out of the box and I sent it back. Is your S new or have you had it for a while?