Applied for A1/S1, only received A1

Hello: my wife is posted in the Netherlands while being paid by a UK employer. To obtain healthcare in the Netherlands she needs an S1 certificate. The guidance seemed to suggest that she should apply for an A1 using form CA3822, and the S1 would automatically be sent. She did so and received an A1, but no S1. What should she do to get the S1? It is now quite urgent, as we really thought the S1 would come along with the A1 . The helpline suggested to send a letter to a postal address for International Caseworkers, but this seems like it would be very slow -- is there an electronic way to proceed?

Hi,
If your wife could complete and return form CA8421 then our International Team will be able to provide her with an S1 if appropriate – she may obtain this via:
Apply for a certificate to confirm you pay UK National Insurance when working in 2 or more countries (CA8421).  
If she needs an S1 for a dependant then we will need a CA8454 – this may be obtained via:  
Apply for healthcare cover in the EU, Iceland, Liechtenstein, Norway or Switzerland (CA8454)
Thank you.