We can't know. You have not provided any useful info like version of AE, system, details about your clip and comp and what have you.
You need to explain your workflow precisely. If you load an image sequence into AE the default frame rate is 30 fps. You may change this in the Preferences or by selecting the footage in the Project panel and then selecting File>Interpret Footage. If you use the Stretch column or time remapping to change the playback speed of a layer in the time line it will work on that layer if the layer is a movie, an image sequence or a nested comp. I suspect user error rather than system problems. If you cannot move the end point or out point of a layer by using the values in the Stretch column then something is wrong with your workflow.
If you have created your time-lapse by sequencing layers or some other means then this technique will not work.
'If you cannot move the end point or out point of a layer.."
this is what i needed. I did not know the sliders above the sequence or comp needed to be adjusted. so simple once you know
thanks for responding!! all fixed now.