from the FAQ as linked above:
DNS has no concept of websites or ads or other resources like images or scripts.
It's main purpose is to translate a domain name into IP addresses.
As a filtering DNS resolver, Pi-hole isn't aware of whether a given domain block would block an entire website or a single ad. It just will refuse to reply an IP address for a blocked domain.
The steps detailed in the FAQ will help you to find out what domains are involved and would possibly need to be blocked or (in your case) unblocked.
However, I can confirm www.nrk.no is working for me, and I also use Steven Black's hosts blocklist, with no extra whitelisting.
Since this would suggest that your issue isn't likely related to Pi-hole, are you perhaps using some ad-blocking browser extensions that would interfere?