How do I unlock my iPad to get horizontal screen

Normally a Restore would be recommended but since I don't know how to do that how about a workaround ? Go to settings> general> accessibility> assistive touch> on. Now to rotate the screen tap the onscreen button. Tap device on the onscreen menu. Tap rotate screen on the next menu. Try rotating the screen. I think a trip to the Apple Store is in your future to have your iPad checked out.

I Know that you found your answer, but this might be of interest to you.

About the iPad Side Switch - Apple Support

The iPad Air 2 is the first and only iPad to not have the side switch. Screen rotation lock and Muting of System Sounds are accessed in the Control Center since there is no side switch on the newest full sized iPad.

This is my boilerplate that explains how the side switch works. I have posted this many, many times when users could not understand why their sound in apps and notifications disappeared or why the screen would not rotate.

System sounds can be muted and controlled two different ways. The screen lock rotation can be controlled in the same manner as well.

Settings>General>Use Side Switch to: Mute System sounds. If this option is selected, the switch on the side of the iPad above the volume rocker will mute system sounds.

If you choose Lock Screen Rotation, then the switch locks the screen. If the screen is locked, you will see a lock icon in the upper right corner next to the battery indicator gauge.

If you have the side switch set to lock screen rotation then the system sound control is in the control center if you are running iOS 7 or iOS 8, Swipe up from the bottom of the screen to get to control center . Tap on the bell icon and system sounds will return.

If you are running iOS 5 or iOS 6, the system sound control is in the task bar at the bottom. Double tap the home button and swipe all the way to the right in the task bar to get to the speaker icon on the left side. Tap on that and the sounds will return.

If you have the side switch set to mute system sounds, then the screen lock can be accessed in the same manner as described above.

If you don't see the lock-rotation icon in the Contriol Center you need to use the side switch next to the volume switch.

I'm not as knowledgeable about the iPad as I am about other things, but I have the Control center totally disabled as I find it superfluous and lock rotation is off - the only thing I do to rotate between landscape and vertical is to simply turn the iPad and the screen adjusts automatically.

Do you have an iPad Air 2 ? This used to be a more common problem when there was a sideswitch. If the sideswitch was set to mute the Control Center would have the anti-rotation icon. If the side switch was set to anti-rotation the Control Center would show mute. The side switch is so small many users turn it on by accident. If you have an iPad Air 2 you should have both the anti-rotation and mute icons in the Control Center.

If you have an iPad Air 2 you should have both the anti-rotation and mute icons in the Control Center.

I have an iPad Air original, not the current iteration.

I have no idea if I have those icons in the Control Center because I turned it off (and I'm not near the iPad right now) I don't need it or want it. I can set either one or the other (mute or rotation lock) in the Settings and I have it set for mute.

Not entirely sure about that: go to Settings > general >

Use Side Switch for: ( choice of ) Lock Rotation OR Mute.

You can only choose one by tapping on it (resulting in a checkmark next to it) - if you choose the other, then the first checkmark disappears.

Edit: the above makes sense as it seems to be a toggle switch - toggling back and forth - or, choice of one or the other......

And:

When the side switch is set to mute the Control Center become lick-rotation and vice-versa.

My side switch is set to mute AND the control center is turned OFF / not activated. All I do is turn the iPad horzontally or vertically and the screen follows automatically. No Control Center or Side switch needed.

Correct. The side switch can only do one function at a time. That's why a long time ago a second onscreen icon was added. So you wouldn't have to go into settings each time you wanted to choose one or the other.

Edit to your edit. The side switch is a no/off switch, not choice switch.

We're talking about the OP who managed to lock his screen. There are two ways to unlock it. The sideswitch or the Control Center. Since the anti-rotation wasn't showing in the Cintrol Center the easiest way is to use the side switch.

slide switch

There is a switch right above the volume switch on the side which can be used to engage the lock rotation or the mute setting (as far as I can tell). I've never used that as I also use the Settings > General choices.

That's how we learn, don't kick yourself. I'm forever accidently brushing the screen turning things on or off. Then I have to backtrack and figure out what I did and how to undo it.

Be sure to stop back in anytime you have a question.

If it's just one gane or app it might that game only works in portrait mode. Then pull up the Control Center to see if Anti-rotation is turned on there. You mentioned you tried the side switch. By rebooting did you mean a reset ? Press and hold both the home and power buttons until the Apple logo appears. Release both buttons. Wait until your iPad starts in it's iwn.

Seems to be stuck in portrait mode irrespective of the app. I also tried the hard reset (using the home and power buttons) and a "reset all settings" via the general settings and it's still stuck. It has never been dropped or banged so I don't understand it. A while back it was stuck in landscape, then I did a reset and it has been stuck in portrait mode ever since.