Solar panels

QrizB

I'm not sure what more we can do until the OP comes back with more info on exactly what is going on.

Ectophile

There were a few non-smart electronic meters that would add up all electricity flowing in either direction.  Those needed to be replaced when installing solar.

If it's a smart meter, then the electricity company may be reading the wrong registers.  They have multiple registers to record usage in (to support things like Economy 7).  But they are so reconfigurable that things can easily go wrong.

[Deleted User]

If it's a smart meter, then the electricity company may be reading the wrong registers.

They are separate registers:

To access the Active Export Register,  the supplier needs to obtain a unique MPAN from the relevant DNO. If anything is amiss, I suspect that problem sits within the supplier’s billing system. As yet, with no response from the OP we are all grasping at straws.