A domicile address requirement means the USPTO does not have a valid domicile address for the applicant. Every trademark applicant must provide a domicile address; the permanent legal place of residence for an individual, or the principal place of business for a legal entity; in the application.
For clarity, you mustn’t list a P.O. Box, a mail forwarding address, or a third-party mail receiving agency as your domicile address. These do not qualify. The address must be a real physical location that constitutes the applicant's actual legal domicile.
The response requires providing a valid domicile address. For foreign applicants who do not have a US domicile address, the requirement to appoint a licensed US attorney satisfies the underlying concern; the attorney's address can then serve as the correspondence address while the applicant's foreign address is listed as the domicile.