How can I document that I am allowed to travel to the UK from Scandinavia using eVisa/BRP? (Denied at the check-in counter)

I am traveling with SAS from Norway to the UK, via Kastrup Airport in Copenhagen.

I am a Chinese citizen. I have a Schengen Visa valid until April. I have a physical BRP card that expired on December 31st 2024. I have an eVisa linked to my passport.

At the airport I provided the staff at the check-in counter with my BRP card, and a printout of my eVisa, and a share code and the link "https://www.gov.uk/check-immigration-status" as explained here.

The staff said that they could not use this information (the share code) and they were unable to enter the BRP number into their systems as it has expired. They therefore said that they could not check me in all the way to the UK. They checked me in to Copenhagen and said that I would have to sort this out at the SAS counter there.

What can I do (or what should I have done) in order to be able to travel to the UK?

The airline is clearly at fault here.

Guidance for airlines is here. It states:

If a passenger holds a digital eVisa, they may no longer have a physical visa or other permission document to inspect. The receipt of a 0A (board) message is satisfactory evidence of their permission to travel to the UK.

They should not need anything, the passport number submitted via API should be enough for them to receive the "board" message.

If that doesn't work:

Where a passenger does not have a valid physical visa or visa exemption document, you may also accept evidence of UK status where this is provided by the passenger via the online ‘View and Prove’ service. In order to provide this evidence a passenger will need to log onto their eVisa account and generate a share code. You can then use the share code (and the passenger’s date of birth) to check the passenger’s status information using the ‘Check someone’s immigration’ status service on gov.uk.

Also, as there have been issues with eVisas, BRPs are still valid even though they expired on 31/12/2024. For instance, Timatic states:

Until 31 March 2025, expired biometric residence permits (BRPs) are accepted if they expire on or after 31 December 2024.