Adding a link returns me to the post page

When I am writing a post and try to enter a link using the menu button at the top, I enter the link, click submit and then I am immediately brought back to the page that lists all of my blog posts. I am also unable to add any media to any post. Note that I had someone create the blog for me so I am a total WP newbie and I don’t understand how to fix this. Any help would be greatly appreciated.