Google Maps not working properly.

I am using upfront Map. The API key is entered so, I’m not sure why it’s not working. Getting the following error in the console. “You have exceeded your request quota for this API.”

Please help or any suggestion why it is happening and how can we solve this. Tried with couple different account creating new API key but no luck. It seems OK at first look but after a couple of refreshes the error shows up again.