It is very frustrating trying to get SSDR to pick up FlexControl. Takes about 1/2 hour fiddling with it before it finally connects. In the process there will be a total shut down of SSdr with an exception. I will go back as former versions do work. I will wait for a fix hopefully soon.
There is a recognized defect in SmartSDR v1.4.16 that may prevent a FlexControl from connecting to SmartSDR. As I have stated on the Community recently (and blind quoted above), we are aware of this issue and are working to find root cause. I am confident we'll have this connection issue resolved in the next release. In the meantime, follow the advice from Ken listed above.
"...go to the Settings>Radio tab and disable FlexControl for a few seconds, then Enable it again, and the Flex Control Knob works again."