First there were a few tweets.
"Just missed about 3 trains at Columbia Heights bc the fare card machines aren't working," tweeted one rider at 8:10 a.m.
"Fare/smartrip machines not accepting debit cards at Vienna and I had to be the one to tell customers because station mgr refused," complained another a few minutes later.
Other riders tweeted that fare machines hadn't been working properly since yesterday.
A little before 9 a.m., Metro confirmed the glitch: "Metrorail fare machines currently experiencing connection troubles with transactions. Technicians working fix. Thanks for your patience."
The problem was intermittent, Metro spokesman Dan Stessel said. "Some transactions were going through without a problem, while some were taking a long time or timing out."
About fifteen minutes later, @WMATA reported that the problem was resolved.
No word yet on why the problem occurred.