But in February, when Ms. LaBelle tried to check her food stamps balance, she got a message that access to her information was “currently unavailable to the residents of Maine.” That interruption, she said, lasted for nearly a month, in which she also lost the timesaving and meal-planning convenience of the app.

Propel, Mr. Chen insisted, has tried to explain its business to state governments and to food stamp contractors. The Propel app is a digital “skin” that works on top of the websites of food stamp contractors, like Conduent. A user taps the app, which is known as FreshEBT, to look up the amount left in the account. On average, users check their balances seven times a month.

Conduent, in another twist, has begun competing with the start-up. The business services outsourcer, which has $6 billion in yearly revenue, introduced its own smartphone app last year. Conduent’s entry, ConnectEBT, has significantly fewer reviews and lower ratings on the Google and Apple app stores than Propel’s FreshEBT.

Conduent’s app is available in Utah, South Carolina and Oklahoma, and offers only basic information on account balances and purchases. But the company said it was beginning a broader rollout this year, and would provide “more features and functions” as it gets states’ approval as a regulated contractor, unlike Propel.

Propel’s predicament is magnified because the food-stamp system’s technology, like many government tech services, is outsourced to a relatively small number of companies.

“It’s an oligopoly game, so there’s often not much choice, competition or innovation,” said Josh Miller, who oversaw the development of digital products in the Obama White House. He added that the volume of data requests from Propel is “tiny” in internet terms.