What problem are you having exactly? 

When you say it only works half the time, is it crashing? Or is it just not connecting?

Do you know the problem is with the app? Or maybe with the phone settings? Or maybe your router?

Do you always have your phone connected to the wi-fi when you attempt to use the app? Remember - it will not work if you aren’t on the same wi-fi as your Sonos system. Make sure you haven’t accidentally turned off wi-fi on your phone.

If you can supply more information then maybe I can help.

J

All good points made by @Chunter.

If your phone has ‘WiFi assist’ enabled, disable it, because it does the opposite of assist.

This behaviour is also sometimes caused by the phone flipping between the 2.4GHz  and 5GhZ bands.  If there is a 5GHz band operating see if you can turn this off temporarily, or ‘forget’ the 5GHz SSID on your phone’s WiFi   Alternatively, purely as an experiment, connect a speaker by Ethernet to your router and see if the problem goes away.  This will give us useful information - it won’t have to stay wired.  (Or do you already have a wired device?)

Thank you for your responses. I believe it’s a IPhone issue. My wife’s IPhone 6+ works and my old IPhone 6 worked “other than the songs skipping short” I have tried resetting my phone, router, and Sonos routers twice and still the same results. It won’t recognize any WiFi networks at all. When I made the comment “half the time that was a separate issue with my IPhone 6 and was a frustrated comment but still was an issue. I just need to figure out how to connect my phone and make it work. I went through all your suggestions and still nothing. Please help again. 
 

Another issue to consider is if you have some security software, perhaps a profile installed by your company’s IT group, that is creating a VPN blocking your particular phone from reaching other network devices. 

Although the intermittent behavior you speak of belies this. I would tend to agree with John B on this, it does sound like a 2.4Ghz vs 5Ghz connection, with the router not properly transferring data between the two bands. 

Have you tried the experiment that John B suggested? In your response, there is no indication that you have.  

Just to add: a “songs skipping short” issue is normally not phone-releated as Sonos doesn’t play songs from/via your phone.