So disscuss with Sonos if it has sense, not with us. It's their technology.
Again: did you connect all devices to one SSID? What are the results?
BTW. The answer you get was already pointed as a solution.
FWIW, none of the suggestions (or veiled criticisms 
) were helpful. It didn’t work for a couple of weeks, then one day, a while after I’d stopped doing anything, it suddenly worked. Whether there was a Sonos or other update or something I don’t know.
So if you didn't upgrade/changed Mikrotiks' configuration, then it obviously was Sonos problem. Conclusion: you should have asked Sonos for a solution.