1972 Deville problems with shifting
 

Just had my engine rebuilt on my 1972 coupe 472ci,back about 6 months ago, everything has been done otherwise like tune-up etc. I took a 30 minute drive, had no signs of any problems with shifting. Stopped at home for 15 minutes and went to leave, and it wouldn't shift out of 1st. Checked fluid levels, they're fine and clean. Just trying to find out a cause of the problem, if anyone knows anything about these classics, any help is appreciated.