Custom Login url does not work

I am using WordPress 4.5.2 and running Mystique theme. I have WPS Hide Login installed, and it correctly hides the default WordPress login page. However, the custom login page doesn’t work and just gives a 404 error. The only way I can login to the Dashboard is by temporarily renaming the WPS folder in the plugins directory to disable the plugin. Once I’m in, I can rename it back and it will continue to protect. But the next time I have to login, I have to do the same thing again. What would cause this, and how can I get the custom login URL to work?

https://wordpress.org/plugins/wps-hide-login/