If you ever change the WordPress Address (URL) or Site Address (URL) in your general settings, you might find you’re locked out of your site.
To restore your site, add the following 2 lines of PHP code to the end of your child themes functions file, change the url’s in the code to your own and reload your browser a couple of times.
Once you’ve fixed the problem, remove the 2 lines of code from your functions file.
If you’re setting up SSL and need to change the URL’s to https, you may try using a method which requires you change the URL’s in your General settings which can result in being locked out of the backend of your installation.