It's been a while since I came here, and I decided to as I have found the issue. As noted, I did have the ISY set to 192.168.1.108 so it was effectively a static IP address without DHCP. This issue was due to a change of WiFi router when my existing one died and I replaced with a new one. I got a cheap one while I waited for delivery on the more robust version I now have installed. In a hurry, this temporary WiFi set itself up with a different IP range (192.168.0.1-255) so the ISY did not and would not be detected. I did see the .108 IP when I did an IP scan including this range and suspected it was the ISY even though the usual ID information was not there. I had chosen the static IP a long time ago as I regularly accessed the system remotely and I guess it was easier to keep it working back then.
So to try to keep this short, it's resolved now fairly easily as I installed the new (TP-Link AXE7800 Archer AXE95) Wifi router and in the process this time, prior to getting numerous items connected, I changed the IP address of the router to the previous range I was using. After getting everything connected, I checked the ISY and it came right back.. a little issue with the Java but now it's all back and I have access to the ISY again.
I am very happy to know that I can continue to use this ISY for my system as I don't have an extensive system, mostly lighting and sensors but I do have fairly elaborate programming and scheduling that I didn't want to recreate if possible. I do also very much appreciate the response on this forum and will continue to check it out and try to keep up with the latest changes with Universal Devices. If I can see a possible need in the future, an upgrade to the new hardware would certainly be something I would consider. I do have to resolve my sign on for the UD portal as I tried signing up but I'm not getting the verification email to do so. Thanks again to all for your help.