Everything was working before the 6600 went to Flex for "improvements" Now no keying the radio on FT8. Using wsjt-x 1.9.1 r8747. I'm not sure what is hosed up.
I'd also second the checking of SmartCat and DAX, it is possible that you have lost the previous settings you had with those applications, and it maybe just a matter of looking what you had in configuration on WSJTX and checking if those now exist in Smartcat and DAX. It s most likely a simple matter of reconfiguration or re-adding ports that may have been removed, also check for the ghosting of com-ports as well.