A Shared Calender cannot be shown on my iPad mini but on iPhone

I could been shown a calender which shared with me on Zimbra server (Version 7.x) on iPhone 4 and iPad 2 with IOS version 6.1.2. However, I cannot found it shown on my iPad mini with same IOS version.The version of Zextra mobile version in 1.6.4 is now using. I have checked the configure on the iPhone and iPad with the iPad mini. It is found same setting defined.

What I can do to get my iPad mini shown also the Shared Calender?

Million thanks

(I have checked with the article, "[HowTo] Sync Zimbra Open Source Edition and an iPhone/iPad", and assure the step is correct)