Google release recently Google Pixel 2 XL and it seems that an issue appears with XenMobile.
In fact, if you have enrolled a Google Pixel 2 XL on XenMobile (tested with latest release).
You should receive encryption related errors “The device does not support encryption features required by the application” when opening Secure Apps.
The problem is known and a fix should be released with 10.8.0 release.
Update 1: Following feedback from customer, this also happen on Google Pixel 2.
Update 2: A Citrix KB has been created and can be found here