We currently use CRM 2015 ( (DB

The current app we install on Apple ios, CRM app version (7.0.4) (

The current version on the App store is  13.20124.17 (we are trying to roll out to ipad ios 14.3)

The current app installs ok but does not seem to work with our CRM backend the document below seems to suggest that it should work with CRM 2015 update 1 

Can anyone confirm that this latest version should work with our 2015 backend I am just trying to see if I am dealing with a compatibility issue or a fault