What is wrong with this code?
if (rightStickVerticalPwm == 0)
  {
    servo1.write(elevatorServoStop);
  }
  else if (rightStickVerticalPwm &gt; 1500)
  {
    servo1.write(100);
  }
  else (rightStickVerticalPwm &lt; 1400)
  {
    servo1.write(30);
  }


You cannot have another comparison in an else statement. You might have meant else if in the last clause.

Clarification if you're not well familiar with C/C++: If you have an if statement, it can be followed by arbitrary many else if clauses and at maximum one else clause which will execute when all other conditions fail. For example:

 int a = 10;
 if( a == 9 ) {
       //Executed if a = 9
 } else if( a &lt; 20 ) {
   //If above not executed, this will be executed if a &lt; 20
 } else { 
   //This is executed if none of the conditions above hold.
   //A pure "else" does not have a condition and only one may 
   //exist in an `if` statement.
 }