Q: Why can I no longer use hdmi cable to connect to the tv

Anyway, with the introduction of ios 8.x, apple stopped supporting older a/v cables. You need to get the latest a/v cable with the correct firmware. There is a little chip in the a/v cable. go to the apple store. Buy a new cable. Verify the cable works in the store.

some people report success with a full factory restore.

Re-boot ipad.

Press and hold the Sleep/Wake button until a red slider appears, then drag the slider. Then press and hold the Sleep/Wake button until the Apple logo appears.  page 128 iPad user manual.

force power down if the above give you trouble.

Hold down both the Sleep/Wake button and the Home button. Ten seconds or more.  Hold until the Apple logo appears.

more details on re-booting:

    http://ipad.about.com/od/iPad_Guide/ss/How-To-Reboot-Your-iPad-Power-Off.htm

Restore to factory settings by loading the latest version of ios that your machine will support:

   Do a full backup of your device.  Twice is best -- cloud and computer.

   "You can use iTunes to restore your iPhone, iPad, or iPod touch to factory settings and the latest version of iOS."

   http://support.apple.com/kb/HT1414?viewlocale=en_US&locale=en_US

   "You can put your iOS device into recovery mode, then restore it using iTunes.:

   http://support.apple.com/en-us/HT201263