Norway+ never made any sense because Norway is a pure rule-taker. To gain access to the EU market, it adopts all EU legislation but gets no say in how it’s written.

So the plus sign was always doing an awful lot of work. Presumably it meant that Britain wouldn’t be a rule-taker but somehow would still get the benefits of a pseudo-membership like Norway does. The problem there was that nobody could explain how this would have been better than the special rules EU membership that the UK already had negotiated over decades.