Texturtle, thank you for the quick reply.
Both PCs are running Windows 10 Pro and the version and build are the same. The last Windows update on both PCs was done in January 2018 and the update histories on the two PCs match.
I did the firmware update on the LS220 last Friday using the PC that is still working but the firmware update should have the same effect on both PCs and the failing pc worked for 2 days after the update before the problem showed up today.
I agree that something is different on the failing PC but I can't figure out what that something is.