The most likely reason you are unable to access the in-game shop, is that either Apple, Google, Steam, Sony, Microsoft or Amazon (depending on your device) is currently doing maintenance to their own store.
Since Gems of War needs to contact THEIR store about any purchases, if they are offline, it means we need to close OUR shop too.
The best course of action is to wait a little while (usually 10-15 minutes, but it can sometimes take a few hours), and then try again.
We do have articles about known issues for certain platforms, that may help with you out.
If the problem persists, please contact us at support here: