I have a variation of this problem: all of my DSN connections don't work. I've tried all the obvious things, and at first I thought it was a problem with Kerbalism 3.14 that 3.17 would fix, but it hasn't.
Here's a screen shot - as you can see, the DSN connections appear to be up and running, but all the probes and craft are uncontrollable (including in flight).
https://steamcommunity.com/profiles/76561198095446214/screenshots/
Any help or advice anyone can give would be great.