Hello Greg,
The latest ADI repository designs for ADV7511 should bring up the HDMI output for both ZC706 and ZC702.
In our earlier desigs we have encountered an issue with the reset system, which created the same problem with the output on the ZC702(and ZED board). On ZC706 we did not encounter this problem.
Another thing that you may want to try, is to double check the device tree. For reference, you can check our linux repository for the latest device tree we use.
Of particular interest, may be the following:
https://github.com/analogdevicesinc/linux/commit/7ebe0e94803d3cfa97ccc0200247f9a10850399c
Regards,
Adrian