My wife was able to start the Roam, from her iOS, not working for me on an Android.

It worked after rebooting my phone.

Yesterday it was not working on iOS but it was working on Android. Rebooting didn’t help

Our Wi-Fi may be crap, but it is the same Wi-Fi. This doesn't make sense.
 

Makes perfect sense to me.  Sonos relies on a good wifi connection in order to offer truly in sync playback through all speakers. It also relies on the router to correctly manage ip addressing and not to double allocate addresses.  If you router allows you can set aside a range of Ip addresses on your network and assign these to your Sonos speakers, that can help.

Having worked in IT support restarting equipment not only solved a vast number of issues but even if it didn’t it got you to a known starting point, which then helps with further diagnostic work.

If you are having repeated problems try submitting a diagnostic when a problem next occurs and post it on this forum for the Sonos team to see.

It makes perfect sense to me too, particularly if the router is perhaps auto-selecting it’s WiFi channels on reboot/startup and has landed on overlapping wireless channel(s) and is encountering interference. It’s often easier to say ‘try a reboot’, rather than asking the user to manually scan and configure non-overlapping channels and setting a channel-width to 20MHz for the 2.4Ghz band, in addition to all the other usual things that can reduce interference.

Don’t forget neighbouring WiFi’s may change their channels too from time to time in some cases. All of course in addition to the possibility of the DHCP server becoming confused over duplicate addresses if they have not been reserved - some routers can be problematic if multiple devices are updated and rebooted and so simply giving things a reboot and another opportunity to acquire a leased IP address can quite often solve those issues.

Also: Tips & Tricks - Resolving random issues impacting Sonos devices.. | Sonos Community

The best thing I have done for my setup is to assign static/reserved IP addresses to each of my Sonos from the router’s DHCP page.

Only took a few minutes to configure. Longer to power down all Sonos, reboot the router to flush the old addresses. Then powered everything back up and my instability, particularly at power flop or update time has been gone ever since.

I’ve moved a few times and this entailed changing ISP’s and and ISP mandated routers. If the ISP’s equipment was stable I did not need to reboot from one year to the next. After some early bad experiences with flakey routers, I always reserve IP addresses. In one bad situation the ISP’s router was very unstable and I had to reboot everything on my network at least once a month. (The Internet was burning with flames about that router!) The day that I was able to replace that router the nonsense stopped.

You started your “rant” (your words) talking about having to reboot your router. However, in your post you also mentioned rebooting a device to resolve an issue which didn’t involve your router. Clearly the problem may be your device sometimes.

Rebooting your device and/or your router is standard troubleshooting. As others have said Wi-Fi signals can be influenced by a number of factors.

Also certain routers can’t handle the complexities associated with Sonos to sync across multiple devices. Most people make the mistake of comparing Sonos which is a multiple point connection over Wi-Fi with a cell phone which is a single point connection device.

Taking the advice of others offered in this thread can be the path toward improved enjoyment with your Sonos. Good luck!!