Radio doesn't work right - no sound except when using phone

I have a 2013 Accord LX, and I've had issues for a while with the USB input
connecting to my iPhone to play music thru the stereo. I could usually get it to
work by doing a few little specific tricks with the phone, but this morning it
stopped playing altogether. The last few days it would display "Loading" and
start to auto play a track, then it would stop, blink, and repeat the "Loading"
and start a new song, and just loop like this over and over. I could stop it by
actually opening the Music app and playing a song myself, but even then
periodically tracks would not load and I would have to keep skipping to get it
to play. This morning, it would do the "Loading" loop, then when I opened the
Music app, it simply refused to play anything. The display showed no activity
evne tho the phone was playing to itself. I then tried switching to the radio just
for music, and nothing happened. The display shows the input change, but
nothing else - no station info, no sound. Every input I've tried has the same
result. The only thing that works fine is using my phone as a phone via the
Bluetooth connection. I can make and receive calls fine, and the sound comes
thru the car speakers. However, I can't use the Bluetooth to play music. My
wife has a 2010 Civic that is currently having the wiring harness replaced
because rodents chewed it up, so I thought I might have a similar problem, but
after lifting the hood, I can't see any visible damage to any wires. I know this
doesn't necessarily mean anything, but is there a way to diagnose this without
taking it to a mechanic? I suspect I know the answer, but I thought I'd reach
out for help first. Any thoughts?