Google Maps recently started charging to use their maps API, meaning that any maps using the API on external websites (like yours) that haven’t updated their Google Cloud account billing settings will display an error. So that’s your short answer right there. It’s not expensive, and you get $200 in credits when you sign up, but it does require a credit card.
A simple free Google Maps alternative
But maybe you don’t need to use the maps API. If you just need to display a simple map of a location, pull it up in Google Maps and click the share icon to adjust the display and copy the embed code to paste into your website. Voila! Done. Free map.
Other map providers
If that doesn’t jive with you, check out some cheap or free alternatives.