Make sure the AppWidgetprovider onUpdate method is called, and your setting the right pending intent. Try to debug and see if onUpdate in called when you add the widget in home screen.
Here is a sample working code..
public class CustomAppWidgetProvider extends AppWidgetProvider{
@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
final int N = appWidgetIds.length;
for (int i = 0; i < N; i++) {
int appWidgetId = appWidgetIds[i];
Intent intent = new Intent(context, MainActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);
RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.activity_main);
views.setOnClickPendingIntent(R.id.button1, pendingIntent);
appWidgetManager.updateAppWidget(appWidgetId, views);
}
}
}