Please deactivate all the plugins not related to the theme, and switch to the parent them if you are running the child one and provide your site admin access to the private area.
I have deactivated all the plugins not related to the theme & I use parent theme. This problem was once again. Then It was solved by updating theme Version: 3.4.0 to Theme Version: 3.5.1. Have any solution without providing admin access?
You need to always have the latest version of the theme to be sure that all our functions are working correctly and it is fully compatible with all required plugins.