I just learned this the hard way. Same story. Kingston MicroSD. Updated firmware. Doesn’t work anymore. Found this thread and it’s at least a month old. Why is this firmware still available?!! I am furious! I bought this player for this very feature and after less than a week it doesn’t work and it was nothing I did but the manufacturer itself!
This was on sale this week, so of course when I went to exchange it, they are all out of them.
Sandisk has made another unhappy customer. Either fix the issue or allow us to regress it back to the old firmware.