Solar not charging, when shore supply removed

Gx system on a canal boat, UK

Solar works fine while the shore supply to the inverter is plugged in.

on removal of the shore supply the solar winds down slowly (over a few minutes) to 0.

then does not charge - needs the shore supply to be connected to allow the solar to operate?

GX/MPPT/Multiplus/Orion/Smartshunt/Battery Protect - all work well wen mains supply is on - a

Solar does not charge when shore supply disconnected - the inverter runs correctly but drains battery rather than using solar

any ideas?

Check the rebulk offset on the mppt.

How else is the inverte programmed?