Appointments+ as a "digital product", not showing up in Shopping Cart

Hi, I have a site that allows customers to purchase products, and then select a date, time and location for self-collection. For the latter, I’ve integrated Appointments+ with MarketPress.

I’ve gone through the FAQ – I understand Appointments+ is considered a “digital product” in this instance, and is hence added to the shopping cart…

However, after several rounds of testing, while I (as a end-user) am able to make an appointment, it doesn’t show up in the shopping cart at all…

Am I missing something?

Any help/ tips greatly appreciated.