Victoria Ho, writing for Mashable:

A huge rush of people signed up for Apple Pay on Thursday when the payment service debuted in China, resulting in system errors for users.

It seems the sheer number of users was too much for Apple’s backend system to handle. According to reports, many people were unable to sign up or link their cards to their Apple Pay accounts.

Sounds like Apple may have underestimated demand for Apple Pay in China. Short term a problem. Longer term, a nice problem to have.

UPDATE: This from Ben Lovejoy’s post for 9to5mac:

Update: Apple has since informed us that the comment by a local representative was not an official statement and has been mistranslated from the Chinese by Caixan. The correct information is that the ability to add cards was being made available on a rolling basis throughout the day.

Sounds like this is managed demand, not unanticipated on Apple’s part.