Lerp coroutine not executing

I'm trying to slide an element to a new position. When 'changeState' executes, it starts the 'elementSlide' coroutine, but nothing happens. I've tried writing the coroutine a few different ways, but have ended up with the same problem.

 using UnityEngine;
 using System.Collections;
 
 public class MindManager : MonoBehaviour {
 
     //Variable to determine if the layer is active
     public bool currentlyActive = true;
 
     //Variable to determine if the layer is available
     public bool currentlyAvailable = true;
 
     //
     [System.Serializable]
     public struct bgPosScale
     {
         public float xpos;
         public float ypos;
         public float scaleFactor;
     }
 
     public bgPosScale[] bgOffset = new bgPosScale[3]; 
 
     public GameObject bgTarget;
     public float bgScale;
     public float transTime = 100f;
 
     //Enumerate the subsections of the Mind layer
     public enum SUBSTATE : int {TOP =0, HEAD = 1, LEFT = 2, RIGHT = 3,};
 
     public SUBSTATE subState = SUBSTATE.TOP;
 
     public void Start()
     {
 
     }
 
     public void changeState(int toState)
     {
 
         if (toState != (int)subState) //Only transition if state is not currently active
         {
             Vector3 startPos = bgTarget.transform.position;//Store BG element's current position
             Vector3 newPos = new Vector3(bgOffset[toState].xpos, bgOffset[toState].ypos,0);//Grab the desired position
 
             subState = (SUBSTATE)toState; //Set desired state to active state
 
             elementSlide(bgTarget, startPos, newPos, transTime); //Initiate coroutine
 
 
             //bgTarget.transform.position = new Vector3 (bgOffset[toState].xpos, bgOffset[toState].ypos,0);
             //bgTarget.transform.localScale = new Vector3(bgScale*bgOffset[toState].scaleFactor,bgScale*bgOffset[toState].scaleFactor,0);
         }
     
     }
 
     public IEnumerator elementSlide (GameObject target, Vector3 startPos, Vector3 newPos, float time)
     {
         float timePassed = 0f;
 
         while (timePassed < time) {
             target.transform.position = Vector3.Lerp (startPos, newPos, (timePassed / time));
             timePassed += Time.deltaTime;
             yield return null;
         }
     }
 
 
 
 }