No trueplay and plus sign with question mark (only one, not two) beside device name

What iOS device are you using?

iPhone 11. 

Ok, so you’ve at least one issue which is likely blocking the ability for you to run TruePlay. If we can get rid of the question mark in the room name, I think TruePlay will show up in your controller.

What speakers are in the room that you’re trying to TruePlay? Is there anything after the room name other than the plus sign and the question mark? 

What other Sonos devices do you have in use?

You may want to try a network refresh by unplugging all your Sonos devices from power, then reboot your router. Once the router comes back up, plug back in all Sonos devices. Give them a minute or two to reboot and reconnect, then open your controller, and check that room name again. Is the question mark still there? If it isn’t, does TruePlay work?

Ok. Nothing else in the room name. I only have the arc and the wireless sub. That’s it. I’ll try and unplug the two devices. It’s a royal pain b/c my Arc is wall mounted and my sub is up high on plant shelf. Oh well. I’ll do that today and see what happens. 

So, that means the Sub is not currently actually connected to your router, through the Arc where it receives the WiFi signal. It is the question mark in the room name. You could try just unplugging the Sub and then rebooting the router, but that may not work...but if it does, then you wouldn’t have to mess with the Arc.