Sometimes the update prompt is not available in the App Store, only the Open prompt, even when you have an old version of the ezccs.
There seems to be a bug in the App Store or maybe better called a glitch. Try this first and if it doesn’t help I’ve included a link to a Google search on the issue.
Touch Settings on the device then touch iTunes & App Store. Touch your Apple ID and log out then log in again. If that does't help try rebooting the device.
Here is a link of search results on the issues with various solutions.
Let me know how it goes. The issues of the App Store not showing or allowing updates has been on issues for as long as I’ve used iPhones. This is not an ezccs issue, I just have to deal with it.
As a last resort you can always delete and reinstall the app.