Arlo Pro 2 camera sync button not responding. Does not flash blue all the time.

[jtsc]

My Arlo Pro 2 VMC4030P camera has no response after pressing the sync button, the blue light does not flash at all. I've bought a pack with four cameras and the base. The other three blink after pressing the sync button but only this one does not. I wonder this is because it's the fourth one to install but after all the sync button doesn't cause any response. Can someone help please?

[TomMac]

Pull battery on the troubled one... reinstall battery...  Does the led on front flash Blue once??

If so , try the Sync button again to see if it starts the LED flashing.. if not the unit may be defective as the led should always flash during an attempt to sync regardless of the number of cameras