I have added several links to wikipedia to companies' profiles, but the information is not showing.
https://wikirate.org/PRA_Health_Sciences_Inc?filter%5Bmetric_value%5D=all&filter%5Bproject%5D=University+of+Nottingham+-+Modern+Slavery+Act+Research+2018
You're adding the full url. You only need the page name. (fixed in the example you posted.)