Car not moving
What do you mean not moving, does the car start normal and the car is not going into gear?????
Did you check the transmission fluid after the radiator change out? Also possible the new radiators transmission cooler is not flowing properly.
Sounds like it may have leaked out the transmission fluid in those 50 km. As suggested by my friend "tennisshoes" check the transmission fluid.
Looking for a Used Avalon in your area?
CarGurus has 11,087 nationwide Avalon listings starting at $1,180.
Search Toyota Avalon Questions
Toyota Avalon Experts