SAN FRANCISCO — Restaurant workers, baristas and small-shop owners across the country lost out on hundreds of dollars in tips this past Saturday when a glitch in the Square payment processing app caused an automatic tipping screen to disappear, according to interviews with several workers and managers.

The error happened Saturday morning, after an apparent automatic software update for the Square systems, workers said. That's one of the busiest times of the week for many coffee shops, and baristas are often used to relying on tips to make up significant portions of their paychecks.

"The timing of it all was just awful," said Charlotte Friend, a barista at Houston cafe Giant Leap Coffee, which uses Square. "Their customer service wasn't available, and it's our biggest paycheck day."

Restaurants, bars and coffee shops are using technology more than ever, and more people are using credit cards or touchless payment methods such as Square and Apple Pay — a trend accelerated by social distancing during the pandemic that was even encouraged by the CDC. The software issue shows the potential perils of relying heavily on technology, which has become more of a necessity as many avoid cash payments.

Digital payments have become standard for dining at restaurants and getting food delivered. Meanwhile, the country is facing a labor shortage and many retail businesses are struggling to attract and retain workers at salaries that pay minimum wage, or slightly above.

"It's precisely moments like this where workers reach their breaking point," said Saru Jayaraman, president of One Fair Wage, a national worker-advocacy group.

Square makes a technology that processes credit card payments and is used by small businesses across the country as their main point-of-sale system. Typically, when a customer inserts a card or taps a phone, the system will process it and then bring up a screen asking whether the customer would like to leave a tip. But on Saturday, that screen disappeared for many businesses.

Square posted updates about identifying and resolving the error on its website issquareup.com on Saturday.

“For about three hours on Saturday, Sept. 18th, our systems experienced an issue that prevented some sellers from being able to sign into their accounts or accept tips,” Square spokesman Marcus Torrey said in an email. “We understand how important it is to never miss a sale and how critical tip collection can be for our sellers’ teams.”

He added that the company apologizes and will share more details on how to prevent similar incidents in the future.

Workers in San Diego, Los Angeles, New York, Washington, Portland, Miami, Houston and other cities confirmed issues with their Square systems to the Washington Post, ranging from the tipping screen disappearing to other parts of their systems becoming unresponsive. Some didn’t realize that the screen was malfunctioning for hours, and others tried to manually reset it with every transaction, with erratic success. Many report the outages lasted at least three hours.

Software glitches are common for any technology company, from big players such as Facebook and Amazon to mobile gaming apps. But in this case, the malfunction had an immediate real-world impact on low-wage workers, who can make as little as $2.13 an hour in direct wages in some states and rely on tips to get by.

Jayaraman said that many businesses are raising wages to try to attract workers but that employees still rely heavily on tips. Workers are already stressed by trying to enforce public health rules and make enough money during the pandemic, she said.

"That is why losing tips right now in this precarious moment on a Saturday for several hours is the biggest nightmare for these workers you can possibly imagine," she said.

Some shop owners are asking for answers, and payment, from Square. Andrew Sinclair, owner of Mad Lab Coffee in Hollywood, said he will pay his employee back for the estimated $150 to $250 in tips he lost out on, but is hoping Square will reimburse him in some way.

It was the busiest time of the week for Buzzed Coffee Truck in Salt Lake City, and owner Trina Perez estimated that her employee lost out on about $150 in tips. Perez said she will pay them for the lost tips but wants answers from the company.

"I am very disgruntled and frustrated because someone needs to take accountability for this issue, and I feel it's really hard for my team to be out that money," she said.

She and other shop owners said they have not received any official communication or explanations from Square. Perez briefly messaged with a customer service representative there, she said, who offered her a discount on a certain amount of payment processing fees — a value she estimates to be about $40 or $50.

The glitches were a hit to both morale and wallets, she said.

“Its been really hard in the service industry with COVID and everything, and that was just, like, an unnecessary little added thing,” she said.