Overview
You are unable to use the Exinda after replacing ASA firewall pair and the IDS with a new FirePower firewall pair in HA. The previous setup had an aggregate L2 switch converting firewall connections to just use one Exinda bridge, but now the firewalls and LAN appear on two different VLANs at this switch. Use of trunks did not work. Only by setting the two Exinda bridges in bypass mode are you able to use the appliance.
Solution
Eliminate the aggregate switch and connect the two firewalls directly to the core switch through the Exinda bridges. This will result in using two bridges on the Exinda
Testing
Check to see if the Exinda is now working as intended.