I have a command not found error in my shell script when I run the code

Question

when I run the code below I get the error message "line 19: checkUser: command not found".

I have tried using shellcheck but I still couldn't fix the issue with the code.

#!/usr/bin/env bash

checkUser() {
    while true; do
       read -p "Enter username you would like to generate: " userName
       if id "$userName" >/dev/null 2&>1; then
          echo "Sorry user exists"
    else
          read -s -p "Enter password : " userPass
          echo adduser "$userName"
          printf "User %s has been added\n" "$userName"
          read -p "Enter group you want to assign user to: " userGroups
          useradd -G "userGroups" "$userName" &&
          printf "User has been added to group %s\n"  "$userGroups"
    fi
    read -p "Do you want to add another user? [y/n] " yn
    if [[ $yn = *[nN]* ]]; then
       break
   fi
done
}
checkUser