John.Id be interested to hear more if there's anyway of sharing the info? IJN has my email address if needed?
I am a serving member of the RAF. The app does not talk to our base medical records. However the base records do talk to the NHS website. If the RN is the same as the RAF your son needs to log onto the NHS website, covid pass and create/login to the website. His covid jabs should be on there. Mine are showing on there, but not on the app.