For 1) In order to purchase gems, please make sure you have not disabled the In-App purchases on your device. You can check it by clicking on the 'Settings' button, then press 'General' and in the 'Restrictions' tab, make sure that the In-App Purchase restrictions are disabled. After restarting your device, you should be able to make purchases.
For 2) Close the game from the background and restart it. You can even try to reboot your entire device and let it connect again. After a short waiting-time, it should work again.