Problem with admin panel

Hi. I ha ve a big problem. I cannot to acces to the admin panel after to have activated the plugin) Now my site in always on easy mantenaince mode. How can I risolve the problem? I’ve tried to delet the plugin on the FTP panel but doesn’t work. Maybe the plugin has modified something on the config file or similar? Thanks

https://www.ads-software.com/plugins/easy-maintenance-mode-coming-soon/