The transmission shifts based on engine speed and vehicle speed (or more
precisely, input and output speed of the trans), and throttle position.  I
believe you may have a power-normal button on this car.  Check to see if it
is in the normal position.  If not, put it there.  It is designed to change
the shift points to either a sporty or economy style of driving.  Also, if
it won't accelerate properly, you may have your foot depressing the
accelerator more, which will delay shifting to the next higher gear.