Further to Jo060’s suggestion, even just rebooting the camera, by pulling the batteries for a while, and reinserting them, may result in restored function. Never hurts to replace with new, but if you know them to be good, because you changed them relatively recently, then a reboot alone may work. As with any complex electronic equipment, they sometimes get in a knot, a glitch of some sort, if you will. In such circumstances it would not be impossible for the control system section to continue operating, but the camera side to have become unusable.
If you are going to pull the batteries, or swap them, you may as well reboot the sync module for a while, just to be sure. If that also fails, you could add rebooting your router.
I hope one of those things mentioned helps. Good luck.