Dick brings up a good point.

Possibly, your Sear and Cocking-Piece 'Notch' surfaces have been stoned & polished or altered.
This could result in the Cocking-Piece no longer being held rearward enough so that the Safety-Lever is free to swing and engage.

As Dick suggested, pulling rearward on the Cocking-Piece may allow the Safety to be rotated into the "Safe" position.

The Norwegian and U.S. Krags are like "Close Cousins", (parts are not interchangeable, but, identical in function).

Attached are some photos of U.S. parts, showing how trigger/safety/cocking-piece 'working surfaces' interact.

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