Error 9 is not a very common error code. But when it hits, whatever you were trying to do is stopped. In most cases, Error 9 comes up when you are trying to upgrade/update your firmware.
Like most error codes, there are a variety of fixes for iTunes error 9. What may work for someone might not work for you. What you’ll need to do is try out all the possibilities.
Error 9 as a possible security software issue, this could be firewall blocking access to specific websites/web resources (like iTunes trying to download something from Apple’s servers). Some other examples note this error as happening due to hardware issues (faulty cable, faulty USB port, accidentally disconnect etc.) So you should eliminate following factors one by one.
USB Port
One of the first things you can try is to change the USB port where the cable connects. This is too basic, but I think you should pay more attention to it.
Cable Disconnect / Faulty Cable
When the cable is unplugged/loose, the iPhone looses connection with iTunes. This leads to a plethora of errors (different numbers) and it looks like Error 9 (while not documented on Apple’s support page) could also be one of them.
Another Computer
You should try to use another computer. This is also a basic thing to try.
Security / Anti-virus / Firewall
If you’ve set up firewall or connecting through proxy/vpn, you should make sure that this is not preventing iTunes from connecting to Apple servers remotely. When you try to upgrade your iPhone/iPad, iTunes connects to Apple, checks for hashes, security keys etc. (a bunch of stuff that it uses to verify that your iPhone or iPad is technically “updatable/upgradable.”)
Hope it helps.
