1787 at 768 kHz?

Hello:

I set up a 1787 eval board SDSP and FDSP to work together at 48 kHz and found I could pass audio through it successfully. I then tried to set up the same board with another project (attached) to use the FDSP only and at 768 kHz and, using the same test "harness", I could NOT get output from the board. I suspect it is something in the hardware configuration but have looked through it multiple times to no avail. Can anyone suggest anything to try to get this working? (None of the other queries I've found here have been helpful yet.)

Eval1787_786kHz.dspproj

1787

768 khz