iOS Untrusted Developer error when testing app
Enterprise and other certificates have to be manually trusted on iOS 9 when they didn't have to on iOS 8 and earlier.

Open the Settings app
Open General
Open Profiles (you won’t see this until after the first profile is installed on an iOS device)
Choose the affected profile and trust it

If you don't see &quot;Profiles &amp; Device Management&quot; then your device needs to reinstall the app or get the appropriate profile from MDM / other enrollment. Also, if your network or system blocks any outbound traffic to Apple servers for time sync, OCSP/CRL or notarization checks, you will see errors or potentially have other challenges to run apps.