Let's review the employees' W-4 information entered in your QuickBooks Online (QBO) to ensure it's accurate. You may have set up your employee as a tax-exempt that's why taxes aren't calucating when running payroll.
Click Workers from the left menu, then select Employees.
Select the employee you want to review.
In the Employee details section, click the pencil icon beside Pay to edit.
In the What are Employee's withholdings? section, select the pencil icon.
Go to the 2020 W-4 or later tab, then review the information from there. Make sure their calculated taxes and deduction are entered in the corresponding fields.
If the information was entered correctly, let's try logging in to your QBO account via a different or a private browser. It's a good start to check if it's a browser issue.
If you get the same result while using a different or a private browser, I recommend contacting our Phone Support Team. This way, they can further investigate the issue and provide additional troubleshooting steps to get this fixed.
You might want to check out these articles to learn more about payroll taxes and payroll reports: