"add links" not opening

hi,
i installed latest version 5.8.1.3 but i am facing the problem that “add new link” is not working. A blank page is appearing with url:

http://concretebasics.org/cb/wp-admin/link-add.php

I tried uninstalling & installing but a blank page (as above) appears when i click “add new” link.
kindly see the issue; am desperate to use this plugin which sounds great
thanks

https://wordpress.org/plugins/link-library/