Problems registering an Auto-entrepreneur with SARLU SIREN

My husband is closing his SARLU and wants to start up a new business as an auto-entrepreneur (different activity).  I am trying to register him on the autoentrepreneur site, but when it asks for the siren number if you’ve already have been registered as non salaried, I put in the siren number of the SARLU and it is rejected because “En effet, le siren renseigne correspond a une societe. Je vous invite a renouveler votre declaration en renseignant votre numero siren.”  He only has this SIREN number, no other as far as I know.  I then tried registering and clicked “non” to non-salaried and his registration was again refused with the following message: “En effet, vous etes deja connu au repertoire INSEE. Vous devez cochez la case “oui” a la question….”.  I don’t know what to do… the only siren we have is the one for his SARLU, we don’t have one for him as an individual.  He did have a business before we opened the SARL in 2009 and that was before the auto-entrepreneur status back in 2006, I’m not sure what status he had and I don’t know what the SIREN number was.  Do you think it’s his original SIREN number that they are asking for?  And if so, how can I find that out?  I searched for him by name on the INSEE site, but nothing comes up.  Thank you for any help