It may be due to a problem with your employee's browser. You can suggest that they use a private browser to access the Workforce. It's good to start the troubleshooting since these browsers don't store cache.
Google Chrome: Ctrl + Shift + N
Mozilla Firefox: Ctrl + Shift + P
Safari: Command + Shift + N
Microsoft Edge: Ctrl + Shift + P
If it works on their end, have them clear their regular browser's cache. It will refresh the temporary files as well as the browsing history. They can also use other compatible browsers to narrow down the possibilities of a browser-related problem.
For now, you might want to email or print a copy of your employees' W2s.
Here's how:
Go to the PayrollTaxCenter.
Choose Employees and click Payroll Center.
Click the File Forms tab.
Select View/Print Forms & W-2s.
Enter Payroll PIN. Click OK.
Click the View Employee W-2 forms for all years link in the box on the right.
Select the employee for the W-2 you want to print and follow the Adobe instructions to open the form in Adobe Reader.
To print W-2 forms, choose File, then Print. Click Save.
To email the W-2, choose File, then Send. Once done, click Page by Email.