Originally Posted by
Andrew R Stewart
First thing I think of is a casing that isn't seated in a stop or the cable inner's head isn't seated in it's spool. Andy
This sounds likely, as it would keep the cable from releasing tension and not able to reach the smaller sprockets on the cassette. If your rear wheel was off recently, something may have gotten pulled out of place when reinstalling the wheel. Check where the derailleur housing loop both exits from the chainstay, and enters the derailleur to be sure it is seated in the stops, and that the housing is completely inserted into the endcaps.