Check if your webpage is using the robots meta tag or the X-Robots-Tag HTTP header to instruct search engines not to follow the links on your page. If you want search engines to crawl all the outgoing links on your webpage you must remove the nofollow meta tag.
Outgoing links marked with this tag will tell search engines not to follow or crawl that particular link. Google recommends that nofollow tags are used for paid advertisements on your site and links to pages that have not been vetted as trusted sites (e.g., links posted by users of your site).