Ac coupling with Magnum 4448 MS-PAE

I am trying to wire up a system similar to the diagram below.  I have tried this with an older grid tie inverter and it works just fine (pv powered 4800).  But I just tried connecting it to a delta solivia 6.6 inverter (I know the magnum 4400 watt inverter cannot couple 6kw, so I only have 3kw connected).  The problem is that the grid tie inverter gets ready to start running, and it gives an external fault.  However when I check the history in the inverter it does not list any new external faults.  It shows faults such as low power, etc from when I turned off the power for a minute, but nothing during the time when I am running the magnum inverter.  I have spoke with support at Delta, but the people I am able to talk to are really not any help with anything other than connecting to the grid (which the system works fine when connected to the grid).  I have also contacted magnum, but they have not replied back yet.

Here is some more information on the system:
1- I did not have the battery management diversion load connected (but this would only effect it when the batteries are near full which they were not).

2- We bypassed the sub-panel and PV performance meter, and connected neutral and ground to the Delta inverter. (I also tried it with just the 240VAC lines connected as shown in the diagram without the ground and neutral).

3- The Battery bank is 5,120 watt hours of lithium batteries, which is probably a little small, but should at least run for a few minutes before they get full.

So I am wondering if there is a way to get this to work with the Delta inverter, or if it simply is too sensitive to operate in this way?  Or is there a way to get this to work?

Also is there a list of grid tie inverters that work better than others in this set-up?  I know my pvpowered inverter works great, but it is a little old, and probably does not meet all the new codes...

Thanks!