2 systems on one app

For the moment don’t Factory Reset anything. We need more information on the intent of this workshop WiFi and SONOS system.

Is he also using UBIQUITI WiFi in the main house? Is there a security need for the workshop to be separate WiFi and/or SONOS? 

What sort of lightning protection is in use? Are there any other network devices in the workshop besides SONOS?

Is this PLAY:1 a used unit that had been installed elsewhere?

I'd really lean to having all on the same wifi and LAN, just set the new AP up with the same SSID settings as the ones in the house and you can then roam between them without having to fiddle your controller connection or deal with two systems on a single controller.

You can even set the new AP in the house and make sure it is working before taking it to the garage.

Apologies we are new to this. What is an AP? And how does one configure such things. This is not a mesh network , purely an extender

The UBIQUITI is an AP (Access Point). That UBIQIUTI device is typically not used by new-bees. Was the main system originally setup by a pro or very experienced person? What model is that UBIQUITI? Is it currently operational?

Nope it was bought by my father in law under his own research without my knowledge. I did mention to him that using WiFi extenders is risky with Sonos . It's a lite 7 

It is not an extender. It is a highly advanced and complicated (compared to ones designed for home use)  access point / AP and can be wired to your home network to provide a variety of services.

If the rest of your network is not Ubiquity you are in for a steep learning curve to get it operational. Start on the Ubiquity site and unless you have a Cloud Key device or that function on another Ubiquity device, download the Ubiquity App. That will give you a limited ability to install and set it up. If you have the Cloud Key you can use it to fully configure the AP and add it to your network. I believe it is also possible to do this over ssh in a text terminal, be prepared for tears and hair tearing if that goes for you as it did for me.

I love my Ubiquity gear for all the advanced capabilities, but I'd sure never give mom one!

Again, why do you want a separate system in the workshop? Is there a security concern? Most people would want the workshop to be part of the house system. This will result in the easiest setup and day to day operation. 

Thanks all. I think we thought it might be easier to set up a standalone rather than integrate. But happy for pointers. Will probably send  for a professional after reading this ! 

I'd seriously consider getting a (to a non-networking specialist) user friendly home unit. There are several quality brands that offer a out-of-the-box mesh (access points not extenders) that will prove to be less frustrating long term.

If you are into networking getting a pure router (no integrated Wi-Fi) and using two or more of the Ubiquity APs would give you a great system. An Ubiquity router and switches if needed make for a very capable and well integrated system that can  expand to security cameras and a lot of other functions.