Apple Pay users in China are encountering problems with the service just a day after it made its local debut. It’s thought the sheer number of users trying to sign up are overloading the mobile payments platform, leaving many unable to register their cards.

Some users are seeing a “cannot connect to Apple Pay” error, MacRumors reports, which prevents them from registering their card and signing up for the service. Others get past this error, but are then unable to verify their cards.

Some cannot even open the Wallet app at all, it seems.

Apple is yet to officially comment on the issue, but one report citing an Apple spokesperson suggest that the problem stems from the sheer number of users who are trying to sign up to Apple Pay at once. The problems should fix themselves once demand dies down.

It’s unclear how long that will take, of course — or whether Apple can do anything to eliminate these issues in the meantime. For now, users are being advised to just keep trying.

China has had to wait a long time for Apple Pay, which made its debut in the U.S. in October 2014. But mobile payments services are already popular locally, with millions using the likes of WeChat Payment and Alipay.