TruHearing aid not playing left channel of audio (in mono) after 16.5.1 update

I have just a right hearing aid (TruHearing, Signia). With my previous iPhone that had iOS 16.1, I could stream both the left and right channel of, say, audio into my sole hearing aid. When I got the new iPhone 14 with iOS 16.5.1, I can no longer hear the left channel of music mixed in through the hearing aid, despite going through the procedures of mono-ing the audio in the Audio/Visual settings. On the old phone, it didn't even matter if it was set to mono. The hearing aid always picked up both channels and mixed them together. Apple suggests I get the hearing aid firmware updated, which I will try. Anyone else have this problem and solve it?