Hi Sarah,
This is a known issue with "Test" emails (clicking the "Test" button instead of "Send" on the Email Send record) using our EU platform, and we are working to correct it soon. The links should work fine for an actual send, and we recommend doing an actual send to yourself and some colleagues to make sure you get the desired result. Once you are satisfied with the actual send, you can clone it and send it to your list.
Thanks for bearing with us as we correct the test functionality!