I removed the cylinder to replace the shift tube. It won't go back in even though alignment looks good. Even after jiggling etc.

 

Welcome to FTE.
What won't go back in, shift tube, or lock cyl????

 

lock cylinder. It should just pop right back in

 

OK, insert the ignition key, turn the switch to the "Run" position, EDIT: insert the lock cyl & align/rotate so the actuator pin aligns with the lock cyl housing access hole, so the actuator pin snaps into the lock cyl housing retainer hole.
Are you certain the ignition switch is properly aligned with its index marks????

 

Absolutely, if you don't the locking button on the cylinder won't let you even start the cylinder

 

Make sure the switch rack is in the proper position , and the spacer disc is indexed correctly . If the column was apart , some alignment issues can happen .

 

The alignment of the switch looks good and also the spacer. I did not disassemble the steering column.