The most common reason for this issue is that you have changed the primary domain, the name of your WordPress site. For example you had your WordPress in http://olddomain.com/blog and it was moved to http://newdomain.com. As WordPress is configured by default to work with a specific domain, after changing this domain, you have to reconfigure it.
For more details on how to edit your WordPress domain name, check this article.
If you are unsure how to make the changes, you can always contact us 24/7 in the Live Chat, where one of our representatives will assist you further.
