I look to be having the same issue. I can get everything working by resetting everything, but volume control only work temporarily. Anyone figure this one out?

Sorry about the lack of update! Good news found a ‘solution’!

Configure the remote of the samsung on the TV as a universal remote like you did before but as follows;

1. Pick home cinema
2. Pick SAMSUNG as the brand (not SONOS!!)
3. It asks you to test and confirm the remote, answer NO until the FOURTH attempt.
4. You can now skip the test, pick confirm.
5. Reconfigure the remote with the playbar ( I suggest you powercycle it first to get a good match)
6. No more issues!

Please let me know if it helps you as well :)

Oh wow it really works! I was having the same problem previously. Hope it lasts...

Tried this but my tv Samsung RU8000 does not provide the option to skip the test after the fourth attempt. It asks for me to put in the model number of the TV. Did that and it still didn’t work. 
 

The Samsung One remote works when I have the remote about a 12 inches away from the playbar. If I move back to the couch it changes the volume intermittently or not at all. Move back close again and it works flawlessly. There is nothing in the way of the remote. Straight shot. 
 

What ticks me off is the lack of support for a solution from both Sonos and Samsung. You call either one of them and they point the finger at each other. SOLVE THE PROBLEM!! It isn’t the batteries in the remote, more power cycles won’t solve it, or taking down more diagnostic information. 
 

I just told the issue above. FIX IT!

Best way I found is similar to some of the suggestions but slightly different. Worked for a Samsung RU-8000.

1. Using your remote, select HOME button
2. Scroll left and select SOURCE
3. Scroll up and then to the right and select UNIVERSAL REMOTE
4. Select NEW DEVICE and then HOME THEATRE
5. In the search field, type SONOS and then select it
6. Select OPTICAL, if a pop up window displays indicating the previous setup will be deleted do you want to proceed, select YES
7. Now you need to complete a test on whether your TV turned on or off.
8. Start the test. When it asks you if the test turned on or off the TV, select NO
9. Start the test again for the second time, this time say YES
10. Your Samsung TV will now say you have successfully connected to you remote. 

It should work flawlessly now. 
 

Why could this have worked? My opinion is that all TV manufacturers have numerous codes that work with their remotes. I know this because when I worked for Time Warner installing cable TV services, when we programmed our remote to work with a certain brand TV, we had to try several codes from the manufacturer before the remote could sync with the TV. I think when we say NO to the first test, the Samsung TV (or Sonos Playbar) goes to the next code for the next test in an attempt to sync the Samsung One Remote with the Sonos Playbar.  There probably isn’t that many codes but different codes my have been issued depending on the date you bought your Sonos. I think the second test used a different code that synced well with the Sonos Playbar.  Just my theory, I could be right or wrong. Either way, it works for me now. I hope this helps you. It’s January 19, 2021 and I bought my Playbar in 2018. Give it a try, it won’t hurt anything. 
 

What puzzles me, if my theory is right, why Samsung or Sonos couldn’t figure this out but that’s a topic for another day.