【Updated: 】
If you've added funds to your balance using a Google Play gift card or other method and the addition isn't reflected, clearing your Google Play cache may resolve the issue.
■ Steps
1. Hold down the Google Play app icon on the home screen of your device.
2. Tap Storage & cache, then tap Clear cache.
3. Tap Clear storage, then tap Delete.
Note: There may be some differences in button names or screen appearance depending on your OS version or device.
If you are also unable to purchase Orbs, please review the following article: [Android]I cannot purchase Orbs! What should I do?