It’s because of some fatal error on your site http://prntscr.com/okhzrv
Check the server error log to find out what error you have. Or provide us with Dashboard and FTP access to your site to check it.
I’m sorry but I don’t see any required plugins installed on your site http://prntscr.com/olcpua and we can’t install any plugin because of the server settings http://prntscr.com/olcrbr
Please, install all the required plugins first. Then if you still have any fatal error contact your hosting provider and ask about FTP access. We won’t be able to make any changes via File manager if the site is locked because of the fatal error, in this case we can edit the files only via FTP.