I got your code to submit. I think your best course of action would be to reset the challenge by hitting the check button repeatedly. This will step you back to what your code looked like finished on step 16. This will remove any potential syntax errors and all you have to do is put your link element back.
I can’t seem to get it to not submit for my side. Can you try pasting your code in your post into your browser? That’s the only thing I can really see happening: all your elements have closing tags, your CSS is correct and it submits for me.
If that last post didn’t help you, one potential error may be your comments. I didn’t grab them in my copy paste because I didn’t think they were in your project. But if they are, you probably need to rewrite /* file: index.html */. While this is the correct code for a CSS comment, html comments are written like this <!-- I'm an html Comment -->. If it is in there, it will cause your code to break.