1993 Tempo extr low mileage-won't shift into 2nd until around 25-30 mph on 1993 Ford Tempo

just started not shifting into 2nd at 25 to 30 MPH and into 3rd around 50 MPH.....RPMs are really going crazy by this point.....downshifts fine.....only use to drive around town.....just had new trans filter and fluid changed and they added a conditioner as difference....could it be the spped sensor or the vacuum ?

Asked by for the 1993 Ford Tempo