Category page not working

Hello,
earlier my website had pages for example “Basics of NMR”. I made a category by the same name and put all the posts in that. However, the category page would still show the same page as the page. Then I deleted the page, thinking that the redirection and conflict was because the page was existing. However, when I did that, the category page no longer appears. Here is the link to the category page.
http://nmrcentral.com/category/basics-of-nmr/
Any suggestions what I should do to recover the category page?
Regards,
Akul.