Hi __sebastian__,
Thank you for participating in the Apple Support Communities. If you are having issues with importing photos to your Photos app, here are a few steps to help:
1. Restart your device to see if the issue is still there: Shut down or restart your Mac - Apple Support
2. Confirm that your device is using the most recent software to rule out the older one: Update macOS on Mac - Apple Support
3. Try the steps here to see if they help: Import photos from a camera or phone using Photos on Mac - Apple Support
4. Contact Apple Support here if you need further support: Contact - Official Apple Support
Have a great day.