How old are the Play 5s?

Which sound bar?

You have no system information in your profile so we need you to tell us here.

If they are the original, Gen 1 Play 5s then they will run under the S1 App.

If they are the newer Gen 2 they will run under the S2 App.

However, the gen 1 PLAY:5s can not be used as surround speakers. They can be grouped with other S1 speakers, but if grouped with an S1 soundbar, there will be a slight delay between the two ‘rooms’. 

Here is a page from the Sonos support site on which speakers are compatible with each app:

https://support.sonos.com/en-us/article/sonos-app-version-compatibility

If the Play 5s are Gen1s they are only compatible with the S1 app.

If you have a new soundbar, Arc, Arc Ultra or Beam Gen 2, it is only compatible with the new app.

You are able to have speakers on your network using separate apps, but you will not be able to combine them. Here is a page you can use to see which speakers are compatible with your soundbar:

https://support.sonos.com/en-us/article/surround-sound-guidelines-and-limitations