Why Is My Google My Business Listing Not Appearing Within the Drop-Down?

Let's look into a few reasons why this could be happening.

1. Make sure that your location is verified.

Visit  https://business.google.com/locations and ascertain that your location is coming as "Published."

2. You might be managing more than 100 locations. 

Google My Business API restrictions prevent us to pull more than 100 GMB locations. To fix this issue, you can divide these between different Google accounts. 

3. If your listing is part of a franchise.. you might receive the following message: "This location belongs to a chain. The Local Post API is disabled for this location". 

In this case, it is to be noted that Google API does not support listings of more than 10 locations.