How to setup Map in Contact Page
1) Get google API key, login to google then go this link: https://console.cloud.google.com/apis/credentials then create a project if it was not created yet!
2) Then create a new api key, take a look:

3) Then clicking on the API key, just created

it will take you to this page

here you will authenticate your contact page: ( your_domain/contact and your_domain/contact/ )
then you save, maybe it will take up to 5 minutes for setting to take effect, please patience
4) Then copy the Google API key and paste to setting in your magento theme, go to MGS -> General Setting -> "Google Map on Contact Page", look:
then Save Config, refresh Cache, wait about 5 minutes and check again