My 64 locked up on me at the range Sat. and won’t open. Thy cylinder turns and the ejector rod didn’t come loose. Any ideas?

Try to cock the hammer while assisting the cylinder to turn. An extruded primer from high pressure (handloads or factory loads) can poke into the firing pin bushing and prevent opening the cylinder. If it is the primer, you will have to push forward the cylinder release while firmly tapping on the right side of the cylinder with a wooden block or hard plastic mallet to force the extruded primer aside to open the cylinder.

Find a screw driver and press the locking bolt. This should get the cylinder to unlock.
Also double check that the rod is turned in all the way, counter clockwise to tighten.
Tighten the cylinder release thumb piece, might be loose and this is preventing you to get the full motion on the bolt.