Can't Message Friend on Snapchat After Accepting Request

I'm experiencing an unusual problem with Snapchat! I just added a friend, and although they can send me messages, I'm having trouble sending any back. I'm a bit puzzled about why we're experiencing this one-way communication, considering that we both accepted the friend request. Is there a setting that I overlooked? Is there a problem with the app? I'm concerned that this could potentially strain my friendship if we're unable to have casual conversations. I would greatly appreciate any insights or solutions!