Audio Engine crashed due to loading Slates Virtual Mix Rack. Client showed audio input and was operateable. Just the audio outputs / returns were silent. Did a hardware restart and system worked again. Will try loading VMR after rehearsal again 
Thanks for flagging this - sorry you had this problem. If possible, might you be able to send transform.engine logs (Software | Fourier Audio) to support@fourieraudio.com and we will look into this. In future, perhaps you can try selecting the chain and clicking ‘Restart Chain’ instead of restarting the hardware.