Why is that car won't move after transmission fluid change?

Answer 1

If all that was done is a fluid change--talke it back to the serviceman who did it! If an automatic has low fluid or filter in wrong, it won't go, and/or cause damage by not getting fluid where it needs to go.

If You changed fluid; check level. Add fluid as needed. If you didn't change filter, then it is not the problem, as it worked on old filter. (Best to change it with fluid, though.)

Also, look for any gross leaks from transmission. These must be addressed, too.

The condition of the fluid would be important before you changed it. The fluid might have been bad, "Burnt". which would mean your trans fluid is bad and now the clutches have gone bad also.

It is always better to change fluid often before burnt smell.

If the fluid has a burnt smell to it, then been changed out. The new fluid will further damage the transmission, ie: clutches completely smooth, no forward or reverse, etc.