Yesterday we had a brief power outage and my ISY is now flashing the red (error) and green (memory) lights and I cannot connect to it via my home network or the portal. I have rebooted ISY twice, checked the connection to my router (only one solid green light) and checked the powerline Insteon interface unit (green light on) . Please help me with next steps to troubleshoot.

Thank You

Please refer to the wiki for front light meaning:

https://wiki.universal-devices.com///index.php?title=Main_Page#Front_Panel_LEDs/Lights

 

Sounds like it's not able to access the network.  Did you have a static IP set in the ISY994 or DHCP reservation on the router? (Note: the preferred method is to have DHCP reservation at the router level and allow the ISY994 to connect automatically - in case you ever replace the router it will connect to the new DHCP table of the new router.)

I'd suggest power cycle everything and perhaps even trying another network cable from the ISY994 to the router. Depending on the cause of the power outage could have impacted the network cable. 

Power down steps:

1. ISY994
2. PLM
3. Router

Power UP steps:

1. Router (wait several minutes)
2. PLM (wait at least 1 minute - check that light on PLM is steady)
3. ISY994 (observe light patterns - review wiki)

Once everything has power again log into your router and see if the ISY994 has connected to the network.