i cant change my friends display names

just recently, i tried to change someones display name and it said "could not change display name, please try again." so i did and it still wouldnt work, so i restarted the app. it still wouldnt work so i restarted my phone and even reinstalled the app. nothing is working and i want to change names. please fix this asap.

morganruscetta about Snapchat, v10.14.1.0