2 things you need to do, Both require a scanner

ck the range sensor selector to make sure it's actually making the transittion from park to rev/drive electrically.

2nd would be ck and make sure you don't have a loss of prime fault, meaning either extremely low on fluid or front pump issue.

All A604 based transmissions automatically apply the low/rev clutch as soon as it's started. That way all it has to do is apply either the underdrive clutch or rev clutch. but by description it sounds like a ft pump issue