That seems odd ;)
Have you, by any chance, turned off the radio on the PLAYBAR because you’ve connected it via Ethernet? The surrounds use that radio signal to connect to the PLAYBAR. Both the PLAYBAR and the PLAY:1s need to have their WiFi/radio turned on.
If not, I’d be tempted to submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, their lawyers get sensitive about GDPR. There’s always the possibility of a WiFi failure.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.