Workforce won't cost you any extra money, Phanson. It's included with your company's QuickBooks Time subscription, so it's not an additional service you have to pay for.
The sign-in error you received typically indicates that QuickBooks can't find an active account for you under your company's setup.
If you're the primary admin, please note that the Workforce account is intended for your employees. However, if you added yourself as a worker or just an employee, ensure you've accepted the invitation that was sent to your email to get started.
For more details on setting up your account and how to troubleshoot sign-in issues, check out this article: Set up your QuickBooks Workforce account.
If the issue persists, clear your browser's cache and cookies, as this can help refresh website preferences and remove accumulated data that might be causing the issue.
If clearing the cache doesn’t resolve the problem, use another supported browser to identify if this is a browser-specific issue.
Let us know if you have any questions or need help.