I want to mention a Instagram page but I can't find it.

If you can't find the Instagram page you want to mention there's a big chance that it's not in the mentions library. 

Just follow the steps in this article about the mentions library and you can add the page yourself. After this, you should be able to find it and mention it in your posts.

If after that you still can't find it contact us support@mediainjection.com and we'll help you.