Thank you for posting in the Community. Allow me to help share some additional steps to resolve the error message you get when accessing payroll.
Updating QuickBooks for Mac usually, do the trick. Since you get the same results, let's check next the URL. Let's make sure that the address you're trying to access is for a web page or file. Please use this link to access your payroll: payroll4mac.com.
If you continue to get the same result, I suggest getting in touch with the Technical Support Team for further assistance.