1) Since yesterday a new firmware is available for the Series III mixers. Make sure that your whole ecosystem is using the latest firmwares. All your units had firmware upgrades in 2019. The update for the EarMixers is especially important! Also check software (UC Surface, Q-Mix, Capture). Very often a mismatch of firmwares and softwares is the reason for problems.
2) Re-establish your network and routing. It happens that configurations get changed and changed and changed, so that after some time nothing is fiting any more. A reset of the configurations will also determin the clocking of your network again, because presets (unvisible) are loaded again. Reset project and scene, reset AVB and USB routing and then connect all units again.
3) Check all units separate. You can connect an EarMix directly to the console and check all functions. Also connect the stagebox to the mixer and check if inputs and outputs work.
One important detail in AVB networking is that all units need FULL routing, which means that you have to assign three AVB streams (two input streams, one send stream) to the NSB 16.8 and two send streams to each (!) EarMix.
Hoep this helps.