My prerelease app has been "processing" for over a week in iTunes Connect, what gives?
We had a similar issue. Uploaded builds were queueing up and it simply said "Processing" with the popup help, “After builds are uploaded they will go through a processing state before they can be used.” Days passed.
Selecting "Internal Testers," making a change, and saving seemed to immediately clear the queue: The latest build was now active and available for testing. I've done this twice with two different apps now.
Update: At this point, all bets are off. It seems "processing" happens when Apple quietly upgrades iTunes Connect and there's nothing you can do about it.
On September 23, 2015 iTunes Connect didn't accept any uploads for nearly 24 hours. The "Internal Testers" trick didn't work. Eventually bumping the version number (to avoid "duplicate binary" error) and re-submitting worked.
The next day, Surprise! iTunes Connect was completely changed. I guess we were all looking at a dead site while they brought up the new version in the background :(
In our case we can still see dozens of "failed" uploads still sitting in the "processing" state. Oh well.
Some people report using Application Loader works better than Xcode for submitting builds to iTunes Connect. You can find it inside Xcode now, under the Xcode menu "Open Developer Tool" item.
Sometimes this works. Sometimes it doesn't. Your milage may vary ¯\_(ツ)_/¯
Go to "Resources & Help" in iTunes Connect. Select "Contact Us" and follow the wizard. I don't think anyone other than Apple can answer this. And this is what we have done in a similar situation in the past.
The solution (as suggested by Apple Support in their response to a request for assistance) is to upload a new binary. I did this via XCode (same revision 1.4, but incremented the Build number from 1 to 2) and it processed almost immediately.
If you get stuck in "Processing" purgatory, increment the Build number in XCode, Archive and Submit to the App Store again. If it doesn't process within 15 minutes, try again.