I was using all in one WP security and White Label plugin in one of my wordpress website. I had custom wp-admin login url. After moving host i realized i cannot login via custom url. Also, wp-admin is not working. I tried editing/deleting .htaccess, rename plugin folder and plugin but no luck. Even tried to disable plugins via php admin.
You can reinstall WordPress manually, don't delete your wp-content folder and unzip the file from https://wordpress.org/latest.zip.
Check this Article https://codex.wordpress.org/Upgrading_WordPress#Manual_Update