Chase customers are having problems using Apple Pay on Saturday, with attempts to pay using Apple's payment platform failing while an "unexpected upgrade" is allegedly underway.

A number of iPhone users who use Chase cards with Apple Pay discovered on Saturday that their payments were declining in stores while using Apple's payment platform. The problem wasn't with the card or the account, but only its link to Apple Pay.

Social media posts spotted by The Verge describe the failures as the card being declined when using Apple Pay. It appears that only Chase is affected, with other card issuers allowing payments as usual, and the Chase cards themselves also working fine.

The Apple Pay System Status page explains that, as of 12PM Eastern, Apple Pay & Wallet is undergoing maintenance, with "some users" affected. The status page adds that some Maryland users "may have issues during maintenance activities."

A call placed to the Chase customer service line resulted in a 15-minute wait time, with agents instructed to tell users Apple Pay is "going through maintenance" that involves an "unexpected upgrade."

The actual reason behind the outage remains unknown, and while it is clear Apple is aware of the issues, there is no timescale for it to be fixed.