With that error, I'm thinking the temperature outside is low. (or was?)
The batteries need 40 - 45 degrees to be able to charge.
Your system, like mine, came with a battery heater for this situation.
What I don't know, is if the heater, which is 12 volts, can come on with the batteries dead.
I would suggest calling Future Sales to get some help recovering from this issue. They are very helpful with our SSF systems.
(574) 262-3688
https://www.futuresalesrv.com/
Please keep us updated on this issue.