iOS Ad Hoc installation via TestFlight failing

iOS Ad Hoc installation via TestFlight failing

I'm getting the following error when I try to install an app via
TestFlightApp.com
"Unable to download application. "helloworld" could not be installed at
this time.
When I first got this error, I thought it might be due to Apple's
developer program being down a few weeks back, so I regenerated all my
certificates using the code signing request on my laptop, then rebuilt all
my provisioning profiles.
I then deleted all the profiles from my iPhone, and from XCode, and I
deleted TestFlight from my phone.
Then I archived the app, uploaded to test flight, gave permission to all
the devices in the profile, and sent the notification emails with the
download link.
When I try to download, the progress bar gets nearly all the way to the
end then the error pops up. This is what I see in the Console during
installation (from the iPhone Configuration Utility):
SpringBoard[67] <Warning>: Killing com.helloworldapp for app installation
installd[53] <Error>: 0x2c6000 handle_install: Install
of "/var/mobile/Media/Downloads/-2429066128781955904/-410631401396950200"
requested by itunesstored
installd[53] <Error>: 0x2c6000 MobileInstallationInstall_Server: Installing
app com.helloworldapp
installd[53] <Error>: Aug 23 11:45:37 SecTrustEvaluate
[leaf CriticalExtensions IssuerCommonName]
installd[53] <Error>: 0x2c6000 verify_signer_identity:
MISValidateSignatureAndCopyInfo failed for
/var/tmp/install_staging.a1ku9y/foo_extracted/Payload/helloworld.app/helloworld:
0xe8008017
installd[53] <Error>: 0x2c6000 do_preflight_verification: Could not verify
executable at
/var/tmp/install_staging.a1ku9y/foo_extracted/Payload/helloworld.app
installd[53] <Error>: 0x2c6000 install_application: Could not preflight
application install
itunesstored[71] <Error>: 0x183b000 MobileInstallationInstall: failed with -1
installd[53] <Error>: 0x2c6000 handle_install: API failed
So I've got brand new certificates and profiles, the profile has the
devices I'm trying to install embedded and I've given permission to those
devices in TestFlight.
I'm at a loss now, I've fixed similar problems to this in the past, so
I've run out of all my usual ideas.
And I've tried increasing the version number as well, (that's worked in
the past) but no luck.