Hi,
we can’t login to your WordPress because Maintenance plugin. Please try to deactivated that plugin (only until we find out whats the error) so we can access to your site and look what is going on. We can’t do nothing without access. You can see on the upper link what we see when try to login.
If you use this plugin
https://bs.wordpress.org/plugins/wp-maintenance-mode/
“User with admin rights gets full access to the blog including the front end.”
Also, in attachment you can see that this work fine from our side (our theme demo). Please try to deactivated some third party plugins that you installed and test this by activated them one by one.
Kind regards