I am developing an Android Application and was looking into Google Places for some functionality within the application. Google has recently released the PlacePicker feature
I had the same problems using the Places API. At the end, I figured out that there are different Google Places APIs especially for Android. Consequently, the API-Key that I was using was simply for the non-Android version.
Generate your key using this link: https://developers.google.com/places/android-api/signup