I've checked my resources to verify if there are reported cases about the missing employee tabs but found none. Let's try some basic troubleshooting steps to get past this hurdle.
First, let's switch to an incognito browser then login to QuickBooks Online. Use one of the following keyboard shortcuts to open a private window:
Internet Explorer: Ctrl+Shift+P
Alternatively, you can clear cache or delete your temporary internet files. You may receive an error when working in QuickBooks Online if your browser is holding too much data from previous browsing sessions. Check out this article to get the complete steps with your respective browser: How Do I Clear My Browser Cache And Temporary Internet Files?
Please let me know how it goes. I'd be glad to provide further assistance whenever you need it. Have a nice day!