Cannot purchase on Microsoft Store, Cannot add money to Family Account - how to resolve?

When trying to add money to my child's account I get an error as follows after clicking "Buy":

Contact Microsoft Support

"We're having trouble processing your payment and we'd like to get it sorted out. Contact us at Microsoft Support.

And then some nonsensical alpha numeric code and a timestamp.

Trying purchase on Microsoft Store on Win 10 Surface gets same result.

"Contact Microsoft Suuport" must be some kind of sick joke because there is no obvious way to contact anyone. Just lots of searches on support site and forums that don't provide any helpful info. Weirdly they seem to have no issue processing my subscription payments (Microsoft 365 and Xbox Game Pass).

Called the only number I could find and it directed me right back to the useless support website.

Anyone have a way to get a real person (or at least functional bot) that can help sort this out? My kid is sad, I'm frustrated and Microsoft is losing out on my kids giving them my money.

:)