Submit dropdown value using Submit button Javascript

My javascript for my Submit button runs properly until I try to get the final value, shown below:

this.submitForm(
    "mailto:msanders2657@gmail.com?"  + 
    "&subject=good news" + "&body=" + 
"Name: " + this.getField("SellerFirstName").value + " " + this.getField("SellerLastName").value +
"\nEmail Address: " + this.getField("SellerEmail").value +
"\nPhone Number: " + this.getField("SellerPhone").value +
"\nBest Time to Contact: " + this.getField("SellerContactTime").value
);

This script works just fine with the first four values, which are just text fields. However, the field "SellerContactTime" is a dropdown list with text options, and attempting to add it to this email causes my Submit button to do nothing.

Can someone tell me why I can't submit dropdown form values and how to solve the issue? Thanks!