One would have to ask the Norweigans.
It's not at all uncommon for State NOTAM offices not to take all of the NOTAM from another country. Our own AIS does not for example take the French domestic series.
Generally speaking the system reflects the idea that if your flight takes you outside the State in which it originates then you will be following a "normal" international flight profile and will be landing at a port of entry.
Which is why you should be taking a briefing from the State within whose airspace the flight originates, not from an overseas source.
Hands up all those who think you get NOTAM from the AIS or NATS websites.
?????????????
WRONG!
There is no officially recognised source of UK NOTAM on the web.
What you get is a pre-Flight Information Bulletin (PIB) which omits the data used by AIS and commercial briefing services to produce a PIB.
While NotamPlot, NotamPro and Notam Check all have a go at producing and presenting the underlying data they cannot succeed until NOTAM themselves are released for download. There is no laid down format for PIB; NOTAM by contrast follow an ICAO defined format and include information specifically designed to permit selection and sorting for inclusion in a PIB.
I and others asked last November for the data to be released. NATS/AIS have no objection to its release, it is the CAA who are holding it up.
In the meantime if you want UK NOTAM you can get them from an AFTN feed or by a leased line or dial up connection to the NATS servers. All of these carry costs which mean they are effectively unavailable to the end users, UK pilots.
Mike