Hi @Rnd.ridgway
Welcome to the Sonos Community!
Sorry to hear of this issue you are having with signing in to your Sonos system.
There is a system registered to your account, but it is an S1 system, and S1 systems do not produce this error message.
It seems likely, therefore, that you are trying to sign into a S2 system, but you are doing so with the wrong email address. Please ensure that you are signing into the S2 app - if that is indeed what is happening here - with the Sonos account to which the S2 system is registered. Please note that you can sign in with any Sonos account, but only by signing in with the account to which the speakers are registered will you no longer see that message.
I hope this helps.