I have an older HW-K950 and had the same problem ever since we moved 3 years ago. Whenever the speakers were plugged in, they flashed the blue light but would not connect. Last night I tried something different, and it seems to have worked.
I did a hard reset on the soundbar by holding both (+ and -) switches on the end of the soundbar in the up position for 10 seconds.
*I did a fresh install of the Samsung Multiroom app from Google Play on my phone. Part of the install requires registering the soundbar to your internet account.
I turned off the soundbar and tried the (remote) volume up procedure for about 100 seconds, no results so I tried the same switch in the down position while I was doing that, I think I saw the letters SHOPH, while the soundbar was still off I tried the sub button down and up a few times. After all of that I got up and checked the back of the subwoofer and the red light was on, I checked the two rear Chanell speakers, and the red lights were on there too. I turned the soundbar back on and I had steady blue lights on all three wireless speakers. This morning, I played sound through the D-IN from an older Sharp TV with no HDMI out. I can't definitively say what fixed it, but it is working correctly now.
I wish I had been more orderly in my attempts to fix this and make it easier to replicate but it was 3:30 AM and I had no idea any of this stuff would even work. Good luck with yours.
*I already had the Samsung Multiroom App on my phone, so I uninstalled it and put it back on.
