network switch not seen by node

Not that this is much help but I had the same issue with my NetGear GS-105eVer2 . I had to go the the site and reboot to recover it. The node at the time was using 3.18.9.0 and I upgraded it remotely to 3.19.3.0 and that is when it disappeared however I did update the same node to 3.20.3.0 remotely and the switch remained visible. 
Denis
 

I at times find the gs switches dont do well with the nodes attached to port1. Place the wan vlan untagged on it. I put the nodes on the 5th or 8th port. It takes a more expensive switch to do proper vlan tagging on all of the available ports, the Hap's have limits too. The edge switch found new and used at an affordable price.