A904 problem

Happy New Year everyone.

I have a 73 Duster, 318 & A904. Recently started driving the car after it sat for about 6 months. The trans won’t drop down into first gear when you come to a stop. I have to shift to neutral or first gear and then back to drive.
We checked the fluid level and made sure the kick down linkage was working.
Anything else we can check before taking it to a shop?

thanks.