Sounds like you need to call Sonos Support directly to discuss it.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Can you describe your network?

If you have the ability to hardwire your Playbar to your router temporarily, Try that to see if it solves your connection issue. If it does, consider how to make it permanent. 

"Nothing to do with the network" pretty much puts an end to most of what we can suggest. Seeing other things working on the network and passing networking tests, while helpful to verify the basics are working on the network does nothing to identify many of the network issues that we see here many times a day.

Sonos does a lot of network stuff that other gear doesn't, does stuff in slightly odd or old ways, and just refuses to cooperate with local networks, often intermittently, all stuff we as users can't directly see given our limited access to Sonos internal data.

I spent a lot of time in the "not my network" camp, much to the amusement/frustration of the loldtimers here.

Moved on to "it may be Sonos acting up with my network" and suddenly years of frustrating issues went away after I made clearly unnecessary** tweaks to my network.

**Unnecessary according to my local logs, troubleshooting and common sense, but without them things just didn't work well. So I did them as advised and my Sonos is now happy.