@Ullitaja it’s hard to let you know what might be going on without knowing more. Obviously if you’re not seeing ads, you won’t get rewards. If you want to check out a longer thing I recently shared, you can check out PSA: Friendly Reminder For People Having Issues with Rewards/Ads
If you want just the official guide on things that might be interfering with ads, you may just want to jump to https://support.brave.com/hc/en-us/articles/360055013431-Why-don-t-I-see-any-Brave-Ads-after-enabling-them-