cant login and logout

Hi there, I need help with one of my wordpress plugins. It worked very good on this website and other websites, but now I have a conflict with my website and when the plugin is active I can’t log in or log out. I have to deactivate it from ftp first. If somebody can help me, please let me know. Thanks. This is the website: https://maranataro.com
and the plugin is this: “sermon-manager-for-wordpress” active on page:
https://maranataro.com/sermons/

https://www.ads-software.com/plugins/sermon-manager-for-wordpress/