Beta from Crashlytics fail to install build on testers' devices

I'm sending my app to testers with Beta from Crashlytics which is an amazing tool to do app testing.

I had every new tester's device UDID registered in my developer account and then distribute a new build.

My testers got email invitation and accessed app's installation which could not be completed on their device. They kept seeing an alert showing up with message:

Unable to download app - MyApp could not be installed at this time - Done / Retry

Testers' testing status are "installed" in my Crashlytics dashboard but they're actually not able to finish installation.

Please help me find any possible factor causing this problem.

Perhaps the provisioning profile embedded in the build has been invalidated. Use Xcode to create a new archive, then use Fabric to upload a new build with that archive.

Discussion:

In my case, I had deleted the provisioning profile in the Apple Developer Member Center that had been embedded in each of my Fabric Beta builds. This caused the app testers had previously installed to immediately crash when they tried to launch it (embarrassing). It also caused the "Unable to download app - MyApp could not be installed at this time - Done / Retry" issue when testers tried to (re)install the app via Fabric Beta. Uploading a new build with my new provisioning profile embedded fixed the issue (each tester had to install the new build).

I've run into this problem back on iOS8 and just recently saw it again for iOS9, the only thing that solved the install issue was for my users to delete any previous version that they had downloaded, restart their phone, and try again.

You can also verify with them if Crashlytics properly installed on their iDevice, I've seen more than once where the configuration profile caused the issue, it's worth removing that (Settings -> General -> Configuration Profile (towards the bottom)) and retrying the install.

This is usually caused by one of two problems:

1. Incorrect provisioning profile/code signing settings. Double- and triple-check that the following settings are the same for the project and the provisioning profile: bundle identifier, development vs. distribution, adhoc.
2. Caching - sometimes, even when you've done everything correctly, things still just go awry. In such cases, you can try: deleting the previous version of the app from your phone, cleaning your project, deleting and re-downloading provisioning profiles, and building the app again.