Shimano sora shifter no longer shifts
I've experienced 2 problems on the Sora shifters- one condition was the cable wear caused strands of the cable to break- eventually all broken strands resulted in functional loss &amp; cable replacement needed. When I disassembled the shifter, I found small pieces of the broken cable strands jamming the ratcheting mechanism. You may be experiencing a similar condition if the shifter cable has been previously replaced w/o a complete overhaul of the shifter. As the strands started breaking- the shift action deteriorates, and no click latching was one of the symptoms.  A second problem found on another Sora shifter that had similar shift deterioration was a result of a tensioning spring used for the return action- the 90 degree bend point of the spring was broken. Without an available replacement part, I finally mechanically "unwound" 1 loop of the spring to create a new 90 degree bend for the part. It successfully has been working for several years now on that bike.