How to Fix WordPress Error Not Available
There are different reasons why this can happen. In most cases it may be a security plugin that has changed the deafult login URL to something else.If you don’t know what the login URL is changed to first disable any security plugins installed on the site.
An easy way would be to connect to your site through FTP and navigate to your plugins folder. Normally you would find this here:
wp-content > plugins
Your can either look in your plugins folder and find the plugin that might cause this issue. And then disable it by temporarily renaming the folder.