There may be a few reasons a device doesn't cache the Client Foilo to your mobile device for offline viewing.

Too many images included in your StickyAlbum  

While you can load any number of images to your StickyAlbum, mobile devices will only save a limited amount of data for offline viewing. 

StickyAlbums are the only template that allow offline caching.  Offline caching will not work with albums that have more than 50 images total in the Folio.

To avoid this, we recommend using no more than your best 15-20 images in your StickyAlbum. Or you can disable the Offline Caching in the Homescreen Details Section if you wish to share a larger number of images.

The mobile device's settings don't allow offline caching.  

In some cases, users may have updated their device settings, which can prevent the StickyAlbum from saving for offline viewing. Typically, this happens when cookies are blocked.

Here are the recommended settings that will allow your app to cache on iOS devices using Safari:

Note green means the feature is turned on and could prevent offline caching.

Prevent Cross-Site Tracking: Set to White
Ask Websites not To track me: Set to white 
Block All Cookies:   Set to white

Note in earlier verisons of iOs this is called Allow from Websites I Visit (iOS 8.1-10)