Let's perform some troubleshooting steps to get this fixed and get you back to working order.
To check if it's a browser-related issue, let's try logging in to your QuickBooks Online (QBO) account through a private browser. There are times that the browser stores frequently-accessed data, thus causing websites, like QBO, to act weirdly.
To use a private browser, here's how:
Google Chrome: Ctrl + Shift + N
Internet Explorer: Ctrl + Shift + N
Mozilla Firefox: Ctrl + Shift + N
Safari: Command + Option + N
Once logged in, go back and try to search for activity again to double-check.