OK, try this:
1) With the same file as above open, hit play, stop, then go to the Mixer. Click the gear icon for the Marimba - first attached pic.
2) You should see what the second attached image shows (including the Jam Blocks patch).
3) The green box is where I usually click to select whatever patch I want to sample the sound with using Kontakt Player's built-in keyboard. You'll see some sort of highlight - like the thinner lined orange box in this pic - once it's selected.
4) Now click around on the keys of the keyboard. Do you hear anything?