I believe this will solve many of the current challenges that users have posted.

[BFGAZ]

Arlo Wireless Security Cameras Multiple Camera Failure Solution:

Restart Arlo Base Router:

• Go to "Settings".
• Click "My Devices".
• Click your Arlo Base device (not any of your cameras).
• Click the green "Restart" button.
• Wait for all 3 of the left side green lights to illuminate on your Arlo base station.
• Click "Cameras" to see if all of your cameras now work.

If that fails, do the following:

• Close Arlo computer interface.
• Remove cameras from mountings.
• While directly next to Arlo router, open battery covers for 10 seconds.
• Close battery covers and confirm that blue indicator on front of cameras flash momentarily. If it does not, replace camera batteries (usually not necessary unless there was a low battery warning prior to camera failures).
• Re-sync cameras individually per user instructions (See below).
• Open Arlo computer interface and confirm that all cameras are working.
• Close Arlo computer interface.
• Re-mount cameras.
• Open Arlo computer interface and confirm that all cameras are working.
• It is very highly likely that you will then need to go to “Settings” for each camera that you reset, go to the bottom of the page for each such camera, and do a firmware update for each of those fixed cameras. Each update takes close to 90 seconds and does NOT require that the camera be near the router but instead it can be mounted wherever it originally was.

Arlo Camera Sync Instructions:

• Sync only one camera at a time.
• Make sure camera is in your hands within 18 inches of your Arlo
• Push yellow sync button on right side of router for ONLY 2 seconds.
• The third light from the left on your Arlo router will flash green, indicating that the router is in sync mode. If this occurs, go to step 5.
• If the fifth light from the left flashes yellow, you pushed the sync button for too long. In that case, turn the router off (unplug it or push the power button on the back of the router).  Wait 10 seconds and then turn the router back on and let it fully re-boot until all three green lights from the left are illuminated without flashing.  This will take about 90 seconds.  Then, follow step 3 again.
• While the sync light is flashing, push the sync button on top of one camera at a time for ONLY 2 seconds. The blue light on the front of the camera will flash slowly for 7 to 15 seconds.  Then, the sync light on your Arlo router will stop flashing and will remain sold.  About 5 seconds after that, the blue light on the front of the camera will flash rapidly for about 10 seconds and will then turn off.
• The camera is now synchronized and you can view it through the Arlo computer interface.

[TomMac]

Holding the SYNC button on base for 2 secs is in the older SW versions... the current version requires a QUICK PUSH only!