Issue with upgrade from Arc to Arc Ultra

Are you sure you used Remove Sub and Remove Surrounds before disconnecting your original Arc?

Did you add the Ultra to your existing system? It’s a common mistake to create a new system when introducing new devices. 

Hi,  no I connected the Ultra, set it up in the app then realised I couldn't see the other speakers, so I powered up the Arc then removed the surrounds and sub so the Arc is now a stand alone in another room. I now have 2 systems 1 one with the Arc and 1 with Ultra. The 300's and Mini just show as not connected and I can't add to the Ultra

You created a new system instead of adding the Arc Ultra to your current system.  Factory reset your Arc Ultra.  Then go to the Settings menu for your other system and choose to add a new product.  Follow instructions from there.  After adding the Arc Ultra, you can add the surrounds and Sub.

OK…

First of all by saying you have two “systems” l hope you mean you have  two “Rooms”.

Just so you understand for the next time when changing a home Theater. First remove the Surrounds and Sub via the app.  Next change the room name of the soundbar being replaced to something generic. This will allow you to use the same Room name for the replacement soundbar.

Moving on.. 

The Era 300’s should not show as a stereo pair. They should show as individual rooms. Then you can add them as surrounds to your Arc Ultra.

Under normal circumstances I would not recommend the following as it is extreme. However, you may be at a point of no return therefore the next suggestion….

If you cannot get the Era 300’s to show as separate rooms you’ll have to Factory Reset them and set them up as individual rooms. Then go to the room with the Arc Ultra and add the Era 300’s as surrounds.

You may have to factory reset the Sub mini and add it to the App as a component if you cannot add it to your Arc Ultra in its present state.

Thanks, I'll give it a go