Hi @MattNash23
Welcome to the Sonos Community!
Your two speakers are configured as separate systems, meaning you must have chosen to set up a new system with the Move while disconnected from the Play:3’s system.
I recommend you factory reset the Move, open the app and ensure it is connected to your Play:3, then allow the app to add the Move to your existing system (it should offer to do so automatically). Do not opt to Set Up a New System at any point.
If, for any reason, you struggle with this process, I recommend you get in touch with our technical support team who will be happy to guide you through the process.
I hope this helps.