Answer
Onboarding invitation links can only be used once and expire after 24 hours. If you click the link and see the message Setup link is invalid or expired, the link has either already been used or it has expired.
If You Have Already Set a Password
You do not need to use the link again. Go to the online app login page and sign in with your email address and password. Use the Forgot Password link on that page if you need to reset it.
If You Have Not Yet Set a Password
Ask the payroll administrator to resend the invitation. The steps differ depending on which app they use.
In the online (web/mobile) app: Open the employee record and go to Employees >> Details >> Online Portal. Click Resend Employee Portal Email. A fresh email containing the employee's username and a password reset link is sent immediately to the employee's email address. The password reset link in this email is valid for two hours.
In the desktop app: Open the employee record and go to the Online Portal tab. Click Resend Portal Setup Email. The employee receives a new email containing their username and a password reset link, valid for two hours.
Once you receive the new email, open the link promptly. A password reset link in a resent email is valid for two hours, and an onboarding invitation link expires after 24 hours and can only be used once, so do not open either in multiple browser tabs or click it more than once.
For more information on how portal accounts are created, see What Generates An Employee Portal Account and Email?