Transmission problem with third gear selection?

I have a 4cx yr model 1998 S/N 4161639 power shift transmission recently it not selecting the third gear when going forward but reverses in third gear.
I also notice it delay to move when the first gear is selected.
I check the main line pressure and they are all reading around 140 psi.
I check all the solenoids and they are getting power.
I check all the relays and they are operating
What should I do.
How can I fix my problem