The following tutorials are created based on Simple Business Directory Pro version.
Auto Populate Title, Description, Thumbnail, Latitude and Longitude in 3 Clicks
For Google Map API key to work, make sure to have both API and Application restriction set to None or restrict them to your domain name and all API libraries are enabled.
Also, from the middle of 2018, Google requires you to add a Billing account. Although, for 99% cases you won’t actually have to pay anything as the free usage limit is quite high for most cases.