I have 5 AD-FMCDAQ2-EBZ dev boards and a design loaded into a Kintex UltraScale KCU105 board. Three of the boards work as expected, however two will not produce any data. Clock is detected in every case. PLL is reported as locked in each case. The firmware and software running on the Kintex board do not change. Power down, swap FMCDAQ2 boards, power up, program and two of the boards never drive any data out of the serdes lanes. I can verify this with a Infinium 8GHz DSO and looking at caps C601/602. For the working boards the data looks nice. For the non working boards there is no signal. I've made voltage measurements for all the supply voltages on a non-working board with a freshly calibrated scope and they are all within 1/2% of expected value. Communication with the 9680 over spi is fine.
Where would you look next?