Victron Battery Protect issue

[choob]

I tried installing one of these today due to the farm staff murdering the batteries.

I can't get it to 'switch on'.

I get the following faults at random when I turn it on and off:

Short circuit (checked, can't find one)
Voltage too high (it's 28.6V)
Voltage too low (as above)

I've set it to cut power at 23.6V and turn back on at 25.6V.

Any ideas?