Looks like your resets are overriding any default styling... when I inspect the element in the browser if you uncheck the border property the fields show up. You probably don't want to remove that reset, as it's likely needed for other things on the site.
What have you tried already? I didn't see any specific styling in your css for those inputs.
You should be able to use something like:
.wpcf7-form input {border:1px solid #000000;}
or whatever styling you are wanting. Is that what you've tried?