My hybrid app built using Ionic and IBM MobileFirst is unable to login after the upgrade to iOS 9 and MF 7.1 when built via XCode and deployed to a device or through iOS sim
When using the MBS, you are basically being served directly by the server. The MBS is inside the server and you open the server IP or localhost.
When using a physical device or the iOS Simulator you are connecting to a "remote" hostname. It could be that the value mentioned is not being translated correctly by DNS.
You can try two things, by editing the worklight.plist file in your Xcode project:
host
property; this usually then allows it to pick a value on its own and seems to work, in iOShost
value with the IP address instead of a hostname