My 7 failed after iOS 12.3 update. Was working fine prior but after update I had slow boot and no voice memo recording. The usual audio IC failure indications. Had it repaired and sorted.
also have a 7 Plus and like OP have no headphone detection but earpods and jack adapter work ok in other iPhones.
Did a very quick dock port swop, still same but wonder if I did this too quick now as was rushed. No audio IC symptoms showing up and have not read anything about the link between audio iC and headphone detection though not ruling it out.
anybody else got any suggestions?