Cameras not appearing

[Charlie35]

Started up a new system today.  4 cameras.  Install went smooth.  All four on line and working.  Strong wireless signal at all cameras.  Brand new batteries.  Then there was a firmware update.  One camera updated and promptly disappeard.  After trying some of the suggestions on this website to try to get it back (re-sync the camera, reset the router, delete the  app), I have now successfully gotten to where none of the 4 are visible nor can they be added even though the LED's indicate that sync with the router has taken place.  I'm out of ideas.   Please help.

[TomMac]

First and easiest thing to try is a power button reboot of the base unit

If NG, you'll have to open the battery door of the camera, go to SETTINGS>REMOVE DEVICE, close battery door, and then bring that camera back as if it was new ( resync )

do this for one camera at a time.