Derailleur not shifting to the lowest "gear"
My early-part-of-this-century Mongoose Switchback "has trouble" shifting to the lowest gear. It works pretty well, shifting between the highest gear and back to the middle gear. It also, in the past, has shifted pretty well between the middle gear and on to the lowest gear.
The H screw (the one on the right) seems to work fine, and I can see it move the "cage" from left to right, but the L screw seems to do nothing to the "cage". (The shifting cable was replaced recently.)
If anyone has a suggestion about getting the lowest gear to function, I'd appreciate it.
I'm not an amateur bicyclist and I'm certainly not a professional -- I just say this so you have a general idea of what I know about bikes.