I have a 2005 Suburban with 250k miles. Yesterday, the key just stopped turning, so I can't start vehicle. I also can't shift it into neutral so I can't move it out of the way.

I have googled, YouTube, and read the manual. I have bought a new lock cylinder to replace the old one. However, I have to be able to rotate the key to 'on'. I can't get the key to rotate at all.

Any suggestions or help?

 

The steering wheel isn't locked. I can turn it 6 inches in both directions.

Is there something I am missing?

 

maybe the key is worn out. if you have another key try it.

I would try getting a new key cut using a code...not tracing the old worn out key

 

Mrs. Cusser's key for her 2005 Yukon wouldn't turn either; I had a new key cut from my own key for this, which gets under 1% of the use/wear of her key. That worked for us. Mrs. Cusser generally uses a "fob" to lock and unlock doors, so hers is used just for ignition.

Note that aftermarket keys cut at the store are a softer metal than factory keys. Best would be to keep one of the original factory keys in storage and use copies for everyday use.