First, the initial P12 message was misleading. There was a bug in the error resolution code which caused it to be shown instead of the correct message.
However, the problem does indeed have to do with Storyboards.
If you’re using Cordova-iOS 6.x, the minimum supported iOS version is 11.0. You need to remove the
deployment-target preference from config.xml - it is currently set to 10. Apparently, iOS 10 can’t handle Apple’s latest implementation of Storyboards.
This isn’t going to solve all your problems. It now seems to get past this error and runs into another one. Have a look at it and let us know if you’re stuck.