Denmark is a poor location for solar. They are pretty far north and don't have a lot of sunny days that are good for solar generation. When they do, those peaks drive energy prices negative. From the article: Over the next 10 years, the official expectation is a very large rise in the amount of solar produced. But that kind of clashes with the reality on the ground – they can’t make money
I actually live in Denmark, and we can produce solar energy just fine. My dad installed rooftop solar 10 years ago, and that thing has 90% of his electricity usage since then. It's still producing at around 85% capacity too.