Some software instruments not making a sound in Logic Pro X

When selecting/previewing instruments in the library library, some instruments are playing as expected yet other software instruments are not making any noise. The level meters are moving as if there was sound coming out, but no noise is made. Yet the next instrument will come through loud and clear.

This is selecting an instrument in preview. Some instruments work fine so it's not an issue of muted tracks and such.

For Example: If I select Fingerstyle Bass or Liverpool Bass, I'll hear nothing as I'm pressing keys. Yet, I go down to the Upright Studio Bass, and I hear the instrument as expected. In Vintage Mellotron, I select Flute, and no noise. I select Flutes right below, and I hear an instrument as expected.