Shifter
I just had a similar problem. The little chrome plastic medallion opposite the button on the T-handle fell off. I glued it on and clamped it accross the T-handle overnight. During the night, the whole internal mechanism drifted right because the clamp was squeezing the button. In the morning, I couldn't even shift into reverse from Neutral. The solution was to take the medallion back off and squeeze the internal plastic thing inside the T-handle toward the button. Now when I press the button, I get enough travel to release the shifter.
Reach down and pull the entire T-handle up and off the shifter. You will see a plastic plunger sticking out of the shaft. Look in the T-handle, and you will see that when you press the button, you are pushing a flat metal spring down to push this plunger. You've got to have enough spring tension to work this. If the T-handle does not sit in the correct position, the plastic sleeve that fits the shaft has been stripped due to improper installation. You can go to advance auto and get an aftermarket nob for $15 bucks or get a new OEM T-handle or a salvage OEM.