The app is probably asking you to update to the latest S1 firmware. What version are you on? 

I would first just check your mobile controller & network meet the requirements mentioned in these two links:

System Requirements:

https://support.sonos.com/en-us/article/sonos-system-requirements

Sonos App Requirements:

https://support.sonos.com/en-us/article/sonos-app-requirements

If you are running the S1 app, the firmware will only update to S1.

@Brewbush,

If creating a new S1 only system/household from full factory reset, note that the initial Sonos product used for that household creation must be S1 compatible only.

You cannot create a new S1 system with a product that is both S1 & S2 compatible. So also see this link, which may prove useful, perhaps?..

https://support.sonos.com/en-us/article/sonos-s2-compatibility

So the exact message the pops up when I click “+ Add Product”

is     App Update Needed.  Update the sonos app to the lastest version.  You may have limited functionality until the update is complete”  Then either update or not now.   So can not add additional items.

I started the system with my Gen 1  Sonos Connect:amp, which seems according to the link above one of the items that requires S1

Even when I try to check system compatibility in the app, it pops up requiring me to upgrade the app.  I assume it wants me to go to S2 (I do not believe it wants to update my current S1)  

I am hesitant to update app since once I do, my assumption is my current 10 year old products wont be compatible.

It sounds like it wants you to update to S1.. the current version of the App is v11.6.2

The devices firmware should be on v11.6.x

So perhaps check that is the case in ’Settings/System/About My System’

maybe updating the app does NOT automatically do S2, I may have solved the issue, we shall see

you all were correct….the update was for the S1 system and was not to upgrade to S2.  After I did this, the “Add another product” was able to be selected and I was able to slowly add my older gen devices.

All the pop ups of “If you update to S2 your old products will spontaneously combust” made me nervous to update anything.

I appreciate all your very quick responses!!  Thank you

On another note….the discounts you get for upgrading components are pretty significant….30%….  looking at your Sonos Arc!!

“Resetting” a controller (a controller option) can work out of this sort of loop. While not a problem in this case, other readers should power down all S2 units while working through this. After the controller reset, take care to “Join an existing system”, don’t start a new system. In my opinion it’s too easy to click on the wrong option here and create a mess.

As a general comment Factory Reset rarely cures fundamental issues and is a waste of time. Before Factory Resetting anything, seek further consult.

If that "your" is directed to the contributors to this thread then I guess you think we are Sonos staff? If so, then just for the record we are all just fellow users.