I got unknown error 21 on iTunes when I try to restore my Ipad2

did the google for you here are some hits

https://discussions.apple.com/thread/3618822?start=0&tstart=0

http://forums.techarena.in/portable-devices/1351249.htm

if you want more hits

https://www.google.com/search?source=ig&hl=en&rlz=1G1TSEH_ENDK367&q=identify+ipa d+model&oq=identify+ipad+m&aq=0&aqi=g2g-sv1g-b3&aql=&gs_nf=1&gs_l=igoogle.3.0.0l 2j0i10i15j0i8l3.143541.147315.0.148650.15.15.0.2.2.0.121.1185.10j3.13.0.#hl=en&s ugexp=frgbld&gs_nf=1&tok=AJBeX1ush6FgeyPb2oiWCA&pq=identify%20ipad%20model&cp=17 &gs_id=7&xhr=t&q=unknown+error+21+itunes&pf=p&sclient=psy-ab&rlz=1G1TSEH_ENDK367 &oq=unknown+error+21+&aq=0&aqi=g4&aql=&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_cp.,c f.osb&fp=c5ff0959a78b1649&biw=1732&bih=792

Connect iPad to your computer via USB while it's turned on.

Open iTunes

Hold the iPad's Sleep/Wake switch (power button on the top of the iPad) down until the "power off" slider appears.

Power off the iPad completely (wait for the progress spinner to disappear).

Hold the Sleep/Wake switch AND the Home button down for a full 10 seconds.

After 10 seconds (the second time you'll see the Apple logo on the screen) release the Sleep/Wake switch while still holding the Home button.

Continue to hold the Home button for another 10 seconds until the USB connection image appears on the iPad's screen, then release the Home button.

A pop-up message will appear on iTunes saying it has detected an iPad in recovery mode, you must restore...

Click on the "Restore" button and the process will begin.

Note that your Apps are not backed but exist in the itunes store. If any are missing they can be re-downloaded.

If unable to restore - and please note this process can take several hours sometimes, come back here. There is a data file on your PC that feeds the <other> section of your datamap. I had a similar problem and on deleting this file and resynching was able to drop my other section back down to about 0.6gig. Interestingly, since I erased it and it has written a new one, the other section remains at about 0.63 to 0.68 gig after resynchs!!

Good luck. Ct

When your ipad is connected in itunes right click its icon and select to Reset Warnings. Go to Edit on Menu then Preferences. click Devices tab and put tick in box to prevent devices syncing automatically. In advanced tab, click on Reset Warnings next to Reset all dialoge Warnings - bottom section - and also click Reset Cache below that.

In the General tab just check that the option to Check for Software Updates Automatically has got its tick in the box.

Also just check uder the Menu/Store that Sign Out is available in black and not greyed out. If it is grey , click on View My Account and sign in, quit then do the Restore as outlined in my other post.

Regards, Ct

iTunes: Specific update-and-restore error messages and advanced troubleshooting

http://support.apple.com/kb/TS3694

 Cheers, Tom 😉

A little bit of info first. Are you able to access <Settings> on your pad at the moment, either unconnected or connected to your PC.

Also go into itunes help menu on your Mac and run the Diagnostics for Network connectivity, Device Connectivity and Device Sync tests. Do them one at once. Post back the results here please. Lets start with some basics with how iTunes is communicating with your Mac and device.

Note:

It may be necessary later to create a new user account with admin privileges and run a device iOS restore through the new account, then when finished go back to your original itunes and restore a device backup from there afterwards.

I keep an unsynced copy of iTunes in my Admin Profile, but use itunes day to day through my own ordinary user account for just such an eventuality.

It may also be necessary, in order to get the restore process working, to turn off any kind of application or system control software running through a third party antivirus or network watch programme.

Many of these programmes place access restrictions on system files and registry keys, database files and folders etc.

iTunes always runs with the user permission token it is opened in. Insufficient <Permission> privileges will cause problems for some processes it might require.

I think the first thing to do is ascerttain the state of the battery. Plug it into a charger and leave it for a full 24 hours. The we'll take it from there.Since the system is scrambled i wouldnot trust any feedback the system is currently giving. 24 hour charge first.

i have the same problem 😟

pad did you fix your ipad?

hey i got the exact same thing running on a mac try conecting to a windows pc it worked for me hope this helps

I got the same thing and I always had problems upgrading my iDevices even without jailbreak. This time I got error 21 when I tried to ungrade my jailbroken iPad 2 and it got stuck in the recovery mode. Whenever I held the power button it would turn off but as soon as i plug it in my PC it the connect to iTunes screen would show up on my iPad again.

I fixed it using redsn0w. I closed iTunes, opened redsn0w -> extras ->pwned DFU. At first the pwned DFU button was grey but I managed to turn the iPad off by holding the power button for about 2ish seconds, and I was able to click pwned DFU from there and my iPad just went back to normal. I didn't try the get out of recovery loop provided by redsn0w so I'm not sure if that works.

I think in general the whole syncing and restoring business is a really turn off. After having my first iPod touch in grade 11 and other Apple products these years, I think I will switch to android next I buy a pad or phone. I had problems with my power button jamming a bit over a month after my one year warrenty on my iPhone and Apple asking for 180 for fix, so I ordered the special pentalobe screwdriver online in order to open it to fix myself. No more Apple products for me in the future.

Galaxy it is then, good for you, time to start thinking for yourself.

The following instructions helped me:

• Power off the iPad completely (wait for the progress spinner to disappear).
• Hold the Sleep/Wake switch AND the Home button down for a full 10 seconds.
• After 10 seconds (the second time you'll see the Apple logo on the screen) release the Sleep/Wake switch while still holding the Home button.