Can't get past WaitForSeconds in my coroutine

So I have a coroutine which should wait 7 seconds, then set a text field to "". However, Debug.Log i placed after the WaitForSeconds call never fires.

 void DisplayUsername(IResult result)
     {
         Text UserName = DialogUsername.GetComponent<Text>();
         if(string.IsNullOrEmpty(result.Error))
         {
             UserName.text = "Hi, " + result.ResultDictionary["first_name"];
             StartCoroutine(RemoveWelcomeMessage(UserName));
         }
         else
         {
             Debug.Log(result.Error);
         }
     }
 
    IEnumerator RemoveWelcomeMessage(Text message)
     {
 
         yield return new WaitForSeconds(1);
         message.text = "";
     }

I used the exact same method to Destroy objects in other scripts but I can't figure out why this never gets through the Wait. Any ideas?

Greatly appreciated.