I have a TI 84 plus silver edition. Won't turn

Remove all four AAA batteries. Press and hold the ON key for at least fifteen seconds then release it. Replace the batteries.

Unfortunately, you can only access RESET from within the menus of the calculator. You will have to remove all of the batteries and let the system naturally reset. The TI-84 Plus uses five batteries: four AAA alkaline batteries and one SR44SW or 303 silver oxide backup battery. The silver oxide battery provides auxiliary power to retain memory while you replace the AAA batteries. Re-install the batteries and reprogram your functions.

TI calculators have an annoying habit of dimming the screen when the batteries are changed so that it appears as if the calculator isn't turning on. Turn the calculator on (or at least press the ON key). Press and release the 2ND key. Press and hold the Up-arrow key for a few seconds and see whether the screen becomes legible.

If that doesn't work, remove all four AAA batteries. Press and hold the ON key for ten seconds. Replace the batteries.

If that doesn't fix it, please append a comment to this post and we'll go on from there.

Remove all four AAA batteries. Press and hold down the ON key for at least ten seconds. Replace the batteries and turn the calculator on.

Check for corrsion on battery terminals AND check batteries are in the correct direction.

Have you tried to reset the calculator?

From page 671 of the TI-84 Guidebook:

To reset the calculator:
1) Remove all AAA batteries
2) Hold down the On button for 10 seconds
3) Reinsert AAA batteries
4) Turn the calculator back on.

Note: When you reset your graphing calculator, the contrast sometimes changes.

You say you changed the batteries. Did you also change the back up battery? It's located in a little door with a screw right above the AAA batteries.

My students have come to me many times and have said that their calculator will not turn on. Most times it is that the contrast on the screen has been turned down and the calculator is turning on but the screen is too dim to see that it's on.

To check your contrast, turn the calculator on, press the 2nd key and the up arrow. This is how you darken the screen. You lighten the screen the same way but you use the down arrow instead.

Ther is no reset button. You have to take the batteries out.

Take the AAA batteries out and take the back up battery out...located in a little door with a screw just above the AAA batteries. Leave the batteries out for about 8 hours. This is how you reset a TI graphing calculator.

TI calculators have an annoying habit of dimming the screen when the batteries are changed so that it appears as if the calculator isn't turning on at all. Turn the calculator on (or at least press the ON key). Press and release the 2ND key. Press and hold the Up-arrow key for a few seconds and see whether the screen becomes legible.

ON, 2nd, [up] arrow to change the contrast. Works 99% of the time....