I had the same error 'till I figured out my problem.
I do not know if you made the same mistake I did but for me, it was a small spelling error that made the huge difference in being able to hit that "Save & Submit Code" button.
Notice in my picture on the bottom left it says:
Change your email input from this:
< input type="email">
< input type="email" placeholder="Email">
Now take a look on Line 5. I did the small mistake of not capitalizing the letter "E" in email (where the small grey line is).
I had typed : < input type="email" placeholder="email">
when I should've typed : < input type="email" placeholder "Email">
Although I do not know why the capitalized E made a difference in moving on because the second I clicked on the Save and Submit Code button the E that I had capitalized changed back to a little e. the heck