Hi @Kb8man
Welcome to the Sonos Community!
I am sorry to hear of the trouble you’ve had with your “frozen” S1 system upgrading itself to S2 - this is an issue we are aware of and aim to fix soon.
I am also sorry to say that you were given incomplete advice from the support agent you spoke to, resulting in an apparently unsuccessful attempt to fix things, where in actual fact it was merely incomplete.
As things currently stand, you have 4x Play:1 devices online and running S2, and they will only be picked up by the S2 app, while the S1 app will only ask for you to install the S2 app. This is actually what we recommend that you do, and that you now just add and upgrade the 1 offline speaker to S2 and continue as is.
If you really want to have all 5 speakers on S1 - not recommended as some services and radio stations will, over time, become unavailable, if they are not already so - please read on.
To do so, however, you will have to repeat the downgrade process that you followed while on the phone with one speaker, with the other 4 speakers.
Once all 5 speakers have been downgraded to work with S1, the S1 app, when opened, will no longer request that you update either the speakers or the app without letting you continue, though further S1 updates may be needed once the speakers have been added to S1. I recommend that you uninstall the S2 app as soon as you have finished downgrading the speakers to S1.
If you get stuck at any part, please call back in, quoting your case number - I have added notes to the case to ensure that the next agent you speak to will understand where you are, and what the actual problem was.
I will leave feedback for the agent you spoke to.
I hope this helps, and apologies again.