I have a Flex 6600 with SmartSDR 2.2.8 and WIndows 10 Home all up to date and working correctly until this morning that I notice that the SmartSDR was some how frozen or nothing coming in, but SmartSDR does function you can click and change frequency, modes, etc. It shows the radio and is connected to the radio, but like nothing is coming in ?
I don't know if this will help but I've often wondered if it is a stuck relay some place and a tap/jolt of the unit will get it back on the air. Otherwise try a shut down including removing all power to the unit. I hate to hear it went down on you and good luck with it. We miss you out here on FT8.