Request not authorized or over querylimit

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C#

Actually i want to find out the lat and long based Address using GoogleMaps.LocationServices API.

code:

using GoogleMaps.LocationServices;
using System;

namespace Coordination
{
    public static class LocationService
    {
       
        public static Location Location (string address)
        {
            var locationService = new GoogleLocationService();
            var location = new Location();
            try
            {
                var point = locationService.GetLatLongFromAddress(address);

                if (point != null)
                {
                    location.Latitude = point.Latitude.ToString();
                    location.Longitude = point.Longitude.ToString();
                }
            }
            catch(Exception ex)
            {
                Console.WriteLine(ex.Message);
            }

            return location;
        }
    } 
}

i had got the the error like "An unhandled exception of type 'System.Net.WebException' occurred in GoogleMaps.LocationServices.dll
Additional information: Request Not Authorized or Over QueryLimit" in the following line in the code

var point = locationService.GetLatLongFromAddress(address);

Please help me

Thank u

What I have tried:

i had got the the error like "An unhandled exception of type 'System.Net.WebException' occurred in GoogleMaps.LocationServices.dll
Additional information: Request Not Authorized or Over QueryLimit" in the following line in the code

var point = locationService.GetLatLongFromAddress(address);