Lookalike Audience is too small

If your lookalike is way too small, it might not be ready yet, since lookalikes can take up to 24 hours to be completely built.

If that's not the case because you've created this audience a while ago, what you can do is broaden the amount of people included in your lookalike audience. If you are targeting 1% of the population in the Netherlands, that will result in a very narrow audience. Try making the audience bigger so that it includes more people.