nmtoken is right, you need to request capabilities from the server. In your case you just need to add gkt (key) parameter with valid key value to the request:
https://gatekeeper1.geonorge.no/BaatGatekeeper/gk/gk.nib_utm32_wmts_v2?REQUEST=GetCapabilities&service=WMTS&gkt=gkt_value
I sneaked gkt key from https://www.norgeskart.no/ site and got the following values (excerpt from GetCapabilities reply):
<ows:Identifier>Nibcache_UTM32_EUREF89_v2</ows:Identifier>
<ows:BoundingBox crs="urn:ogc:def:crs:EPSG::25832">
<ows:LowerCorner>-2000000.0 3500000.0</ows:LowerCorner>
<ows:UpperCorner>3545984.0 9045984.0</ows:UpperCorner>
</ows:BoundingBox>