Can't pass Learn HTML Forms by Building a Registration Form, Step 7

Hi,
not sure there is a bug stopping me from passing the step or I have done wrong something.
It keeps giving me a message

" Sorry, your code does not pass. Keep trying.
Hint: You should use the body element selector."

Question:
Step 7
To spruce the project up, let us add some CSS. Begin by giving the body a width of 100% , and a height of 100vh .

My answer:

.body {
  width: 100%;
  height: 100vh;
}

Hi there. You aren’t targeting a class, so you don’t need the . before body!

I have tried different way,
with or without the " . "
the message would still show.

It works for me without the .

hmm,
that’s really strange,
I have to press restart the step to redo it again then now works.