I have logged in and check your site. It seems that there is a plugin conflict which prevents the mobile icon from working. This could be caused by a 3rd party plugin. You could try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
If the issue still exist, please re install X theme and Cornerstone. There might be some files that were corrupted. You can review our update guide and see the Manual Update section to re install X.
Please let us know how it goes.