Why won't it play music on microSD card?

I can copy hundreds of songs from the Windows PC to the microSDHC card.

They all remain visible in Windows Explorer.

Only the first song copied onto the player is visible on the player. It is also the only song that will play.

As I said, I tried this in both MSC and MTP modes. No difference.

I assume I can buy another microSDHC card. Class 4, 16 GB or less, as far as I know.

This is the 1st revision of the Sansa Fuze.