no longer able to cannot connect iphone to stereo amplifier

Iphone SE running 18.3.2.  Have aways been able to connect iPhone to stereo amp using 3 way RCA cable to lightening adapter lisening to music through stereo speakers.  Not anymore.  Two senior Apple advisors - lots of time -not resolved.  Nothing wrong with input jacks on amp.  Tried different lightening adapter.  Am able to connect iPhone to headphones using same lightening adapter -no problem.  My wife's old 6S plus -works fine connecting to amp with same wiring.  When I say not able to connect -I mean no music comes out through speakers.  I deleted and reloaded the music app -no good.   I suspect the problem is connected to a software update.  

Thinking of putting my music library on an iPod.   Anybody else run into this problem??  Thanks