Try pushing the TNR button on the remote . This should unlock it.
No TNR button on the remote, have the older style. From what I recall, it was something like reversing the batteries to short the chip to reset it, but can't get it to do it. Sounded weird to me. Ugh, or was that a denon remote? Too much gear sometimes.
My issue is the source selector is broken off, so now I'm stuck in one mode and can't get out.