I did, it seems you didn't. Let's show you your code structure so you can see it:

 public class Sum
 {
  public int GetSum(int a, int b)
  { 
      if () {
      }
      else if (){
         for () {
         }
         else if () { // this is the one that's wrong, it comes after a for, not an if or an else if
           for () {             
           }
         }
    }
    return
  }
}

You misplaced some }. Read this: https://docs.codewars.com/training/troubleshooting#post-discourse and use markdown formatting in your code so it's easier to read when you post it here, please.

You have an else after a for. Reading the error message helps:

src/main/java/Sum.java:11: error: 'else' without 'if'
         } else if(a < b){
           ^
1 error

It tells you exactly in which line you have the problem. Before your else if you need another else if or an if.