Hi,
You have a fatal error related to function get_author_permastruct.
This function is not used in QSM plugin.
If you are able to access your WordPress admin, please clear your cache plugin’s cache content and see if you are still experiencing the same issue.
You can proceed to find out which plugin is causing your issue, by disabling one plugin at a time and clearing your cache content.
You can also check whether it is an issue with your theme, by switching to a WordPress default theme and clear your cache content.
Regards,
Kriti