No penetration test is on record
There is no penetration test on record, or you have not said when the last one was. Section 500.5 has the carrier test its own systems at least annually, by a qualified internal or external party, and the questionnaire asks a vendor for evidence of the same from the last twelve months. A reviewer does not accept a description of the programme in place of the report; they ask for the report, and its date is the first thing they read.
To fix: Commission a penetration test by a qualified party, internal or external, that is independent of the team that built the systems; keep the report as an evidence record and attach it here. The report can be redacted; the date, the scope and the summary of findings cannot be.