Google recently implemented new billing rules for Google Maps.
In order to display maps on a website, you need to not only have a correctly configured API key, but the account used at Google also needs a billing account set up with a card assigned for any billing.
This has been announced in a few places, and if you click through the links provided on the greyed out maps and/or look at the details in the console you’ll see more descriptive warnings/explanations.
See: https://cloud.google.com/maps-platform/user-guide/pricing-changes/
In summary: the free tier has gone. You get $200 credit. Any usage above that is billed, so you need to add a billing account/card.
