How much do you want the non freeview polarity?

Swing the LNB 90 degrees and you'll get freeview on Horizontal polarity, but not SBS on vertical.

Those oval ex sky lnbs are failing a lot recently so the answer really is to get another lnb.

It would make sense to re check your options in the computer software though. You need to be able to send the differing voltages up to the lnb to change polarity, so you need to ensure some silly setting is not blocking that from happening.

Also make sure you have the right settings in there for the NZ freeview transponders. If they are out then it will appear that it can't find anything. Someone suggested subtracting 5 off every frequency to account for the 'slip' of the failing lnb. That's a patch for a failing bit of equipment, but might help sort out if everything else is working etc.

There are no other devices using the lnb/satellite dish?