Ionic v1 Enterprise App No Longer Installs on iOS

I've got an Ionic v1 app that was built for iOS before Ionic 2 was a thing. I used Xcode to archive the app for Enterprise distribution, so it could be installed on devices for testing. This was all fine and good until some time last week, when we noticed that the app would no longer install on our iOS devices.

What happens now is that you can click the same link in Safari to download the same .ipa file to the same device as it was previously installed on, it will start downloading to the home screen, then when it reaches 100%, the progress wheel disappears but the icon stays dark. Tapping on the icon gives the following error:

Unable to install "App Name"
Please try again later.

I've tried...

• updating my Ionic CLI to the latest version
• installing the Ionic-v1 toolkit
• updated all of the NPM packages
• run npm audit fix
• fixing a few of the Xcode warnings (not they they've ever mattered in the past) about deployment target, icon sizes etc.
• completely removing the iOS platform and re-installing it
• signing using a different team
• letting Xcode automatically manage signing
• ensured I'm building with a Developer profile (not Distribution)

...but haven't managed to find any fixes at all. Does anyone have any suggestions as to what the elusive issue might be?

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Plugins in use:

• cordova-plugin-camera
• cordova-plugin-compat
• cordova-plugin-console
• cordova-plugin-device
• cordova-plugin-file
• cordova-plugin-file-transfer
• cordova-plugin-inappbrowser
• cordova-plugin-network-information
• cordova-plugin-splashscreen
• cordova-plugin-statusbar
• cordova-plugin-whitelist
• cordova-plugin-x-toast
• cordova-plugin-sqlite-storage
• cordova-plugin-deploy
• cordova-plugin-keyboard
• mx.ferreyra.callnumber

IMHO this is more of iOS signing issue than of ionic, double check that the provisioning profile is not expired.