Welcome to the QuickBooks Community and thank you for choosing QuickBooks Online as your accounting software. Let's perform troubleshooting steps to make sure you can get started with payroll without any issues.
Sometimes a cache full of history and temp files can cause unexpected behaviors, such as Get started button from the Payroll section doesn't work. I recommend logging in to your QuickBooks account using a private browser. Then, try to click the said Get started button from there. This is to rule out the possibility of a webpage problem, and private browsing doesn't keep local files or cache.
Use these keyboard shortcuts based on the browser you're using:
For Firefox or Microsoft Edge, press Ctrl + Shift + P.
For Chrome, press Ctrl + Shift + N.
For Safari, hold down Command + Shift + N.
If it works in incognito, you'll have to clear the cache of your regular browser. This removes the history or log of sites so you can begin with a clean slate. If the steps above didn't work, use another supported browser as an alternative.