Depending on configuration and hosting environment your urls may need to have .aspx at the end. So for a page named "My Dog Skip" you might set the url as
See also information about rules for friendly urls in the seo article.
For any pages currently not working go into page settings and make sure the page has a unique url and save it again if you need to change it. Then make sure that no unintended redirects were created, and delete them if there are any that should not be there.