Edit/Insert Link does not work

Hi Lollie tot did you try the following?

• First, make sure the plugin is up to date
• Second, have a look around the forums for a similar topic as your problem may already be solved
• Third, to test what’s wrong, disable all your other plugins and switch to the default WordPress theme.
• If the problem does not go away, open a support topic, if not, figure out which plugin is the cause of the problem and open a thread mentioning both plugins

*taken from new topic guidelines link: https://wordpress.org/support/topic/please-read-and-follow-the-following-guidelines-before-opening-a-new-topic-1

Also are you able to add links in your posts or pages?