url alias not working when logged in as admin
After dealing with this exact issue for a while in drupal 8, this thread made it click as to what the solution was.

For me, it was my choice of detection for the language that was causing the issue.

Go to /admin/config/regional/language/detection

And make sure that the only checked is the "selected language"

I had the User method checked "Follow the user's language preference." and that was what was causing the issue.

Now this might not work for a multi language site, but my site was originally in danish and I only wanted to have an english version.