Does your app work fine on iphone which have iOS 10? YES
On iPad (8.1) are you using any cloud sync? ICLOUD
Exactly when your app crashes on iPad (On launching or after entering master password)? ON LAUNCHING
For testing purpose do the following:
Also, turn off internet connectivity on iPad and try to open Enpass app. NOT WORKED
If you have all of your latest data on iphone then you can try re-installing the app from ipad and then try to open. NOT WORKED