Greetings paulbigg,
It sounds like you are having issues playing multiplayer on Apple Arcade. We know how important this is for you, and you’re in the right place to find a resolution.
Have you tried a normal restart of all the devices at the same time? This simple step can resolve issues like this. How to Restart your iPhone.
We also recommend all your devices are updated to the latest iOS version. Then test to see if the issue has been resolved. Please let us know what happens.
As with any update, it's always a good idea to create a backup beforehand: How to back up your iPhone, iPad, and iPod touch.
How to update your iOS device: Update your iPhone, iPad, or iPod touch.
Cheers!