My plugins are updated, my WordPress core is upgraded, and I don't have anything too fancy on the website. Yet 'Screen Options' is missing. Where should I begin troubleshooting?
See if there are errors in the developer console (F12 on most browsers)
If not, disable all plugins. If screen options return, enable the plugins one-by-one to see the offender.
If that doesn't help, switch to the default theme to see if that's the issue.