Option settings don't save

When I go into Settings tab, change an option (such as who can see auto-posting options), and then click Update Settings, I end up at /wordpress/wp-admin/options-general.php?page=NextScripts_SNAP.php with a 404 error. When I go back to settings, none of the changes have been saved.

https://www.ads-software.com/extend/plugins/social-networks-auto-poster-facebook-twitter-g/