USB music not working?

[SVonhof]

First post. Wife and I bought a used 2015 Ultimate Coupe and I brought a flash drive with me on our first trip into the foothills and it was working fine and then started skipping from one song to the next on the display and wasn't playing music. We removed it and used Bluetooth via my phone the rest of the trip.
I have tried a different flash drive, thinking that was the cause but now it doesn't even pop-up on the screen as recognizing the flash drive.
I only have MP3's on the flash drive, they are all in various folders based on the artist name and album.

Are they any limitations to the size of the flash drive or speed of it that might be causing the problem?

Thanks for your help.

 

[Mcc]

If you plug your phone in via USB port does it work? Might be the port.

 

[SVonhof]

Plugging my phone in starts up (phone is charging) and then says it is not a compatible USB device (Moto G5+).
Put the flash drive in and it says "Reading USB device" and then that goes away and the button for choosing it for audio never lights up.

 

[SVonhof]

I put the original one back in and it seems to be working, will update later if it starts flipping through the songs again. It is an 8gb MicroSD card in a USB adapter.

I don't know why the other flash drive (32gb flash drive) would not work though.