OAK BROOK, Ill. (AP) — A McDonald’s promotion for free ice cream cones to celebrate National Ice Cream Day went awry over a glitch with the fast food giant’s mobile app.

McDonald’s offered a free vanilla cone to its app users Sunday. But after several users complained to McDonald’s on Twitter that the app wasn’t working, McDonald’s told them to instead simply ask the cashier to honor the promotion. McDonald’s tweeted that the company was trying to resolve the issue and promised to have its app “back online soon.”

A representative for the Oak Brook, Illinois-based company apologized Monday for the “technical issues” but didn’t respond when asked if the app was functioning.

McDonald’s is set to roll out a new app aimed at improving the speed of orders later this year.