Hi @Keith_Ewing,
I have just reviewed the previous thread you had open with us (Crashes, crashes, crashes...!) and to me it looks like your network might be causing this issue.
We have often seen ISP provided routers (such as your AT&T one) cause issues with multicast. Roon uses multicast technology to communicate with devices on the network and if the router is not properly passing this traffic through, then similar symptoms can occur.
Have you tried using a standard consumer-grade router yet such as TP-Link/Netgear/Asus? If you have any of these routers around the house, can you try using this instead of the ATT UVerse router? If the ATT UVerse is a modem/router combo my suggestion here would be to use just the modem aspect of the combo unit and try a regular router connected to the Etherent out on the UVerse modem.
Also, how is your Thinkpad connected to the network here, if it is on WiFi is there any change if you connect it via Ethernet?
– Noris