have a Partner's account but every time i try to login with my Sophos Id and claim my Firewall in the Partner's Dashboard. It always give me this error after I sign in:

Hi cobranet,

Thanks for reaching out to the Sophos Community Forum. 

I'd suggest raising a support case with our Customer Care team. I suspect there may be a conflicting customer record, which may be causing issues with firewall registration. 

A case can be opened from the Sophos Support Portal, or by calling our regional support phone numbers.