I removed a device (ipad) from my list of devices but when i try to reset the ipad it still asks for the apple id and password and it tells me the id cannot be used to unlock the ipad.

Activation Lock

If you purchased, were given, or found a device second-hand, then it is useless without the Apple ID and password to which it is locked. If you don't have it, can't remember it or cannot get it, then the device is useless to you. If you are the original owner then take the device, a copy of your purchase receipt and identity proof to an Apple retailer where they may be able to assist you. This is also true for devices of deceased persons. You will need a certified copy of the death certificate, proof that you are the heir, proof of ID, and proof that the deceased was the legal owner. Note that getting around the Find My Phone activation lock may not be possible.

     Find My iPhone Activation Lock

     If you can't activate your iPhone - Apple Support

If this is a used device, you will need to contact the previous owner to have them log out of iCloud or go to iCloud.com/Find My Phone and erase the device, then remove it from their account. If you can’t do that, the device is useless.

Activation Lock - Turn off Find My iPhone 

If you are the original owner, take the device, the original purchase receipt with the serial number, and a photo ID to the nearest Apple Store.

Genius Bar Reservation US

or contact Apple ID Support. They will need to see the original purchase receipt/paperwork also.

Apple ID Support

Apple ID Support (2) 

Apple Support by e-mail or chat         Select your device, Battery, Power and Charging, then Power adapter not working to get a chat option. 

Apple Support using Twitter

Or fill out and submit this form.