Links won't work on posts or pages

Hello, very new to this but I’ve searched through the link threads and haven’t found anything that has helped so far.

When I post a link to an external site on a post or a page, I do it on the html template but as soon as I click the visual one it won’t show up, and when I got back to html it isn’t there anymore. I have tried updating as soon as I type it and it still does the same thing, whether I click on the visual template or just “preview changes” it is gone. I’m using the Swagger 1.0.7 theme by Jason Bobich, not sure if that has anything to do with it.

Any help would be much appreciated!