Transaxle troubles

Need a little more information.

Is the shifter locked up and unmovable?

Sounds like the linkage for the shifter isn't connected properly to the transmission. If the rod can be disconnected from the transmission, see if you can switch gears at the transmission manually.

Does the shifter move normally but nothing happens (stays in park)?

Linkage problem

Shifter moves normally and you can see it switching gears on the side of the transmission?

Bad transmission, low/no fluid, lever disconnected inside the tranny housing, several other possibilities which you would need a mechanic to locate and fix, usually by removing the transmission.