Some Starbucks customers looking for their cup of Joe Tuesday morning were out of luck.

The coffee chains' payment system was down and baristas were unable to complete transactions.

"As part of our normal course of business, overnight we worked to install a technology update to our store registers in the U.S. and Canada," the company said in a statement.

Some baristas told CNBC that the outage began Monday night.

"A limited number of locations remain offline, and we are working swiftly to resume full operations in each of these stores," Starbucks added. "The stores will remain open during this time and, as always, our partners are prepared to take care of our customers to ensure they have the best experience possible."

The issue, first reported by Twitter users, is affecting chains across the U.S. and parts of Canada. For some locations, the registers in-store are working, but their mobile payment system is down.

Tweet Ally

While some locations stopped serving coffee completely, others offered patrons a free tall beverage.

Tweet 1

Tweet 2

Tweet 3