Clear your cache in your browser settings (Privacy & Security Section).
Enable cookies in your browser settings (Cookies Section).
Restart your computer.
If you are on a district issued device, call the FCPS HelpDesk (381-4410) and explain the steps you've attempted to fix the issue. For district owned devices, having FCPS clear the student profile off the machine may resolve the Authorization issue.
Savvas Troubleshooting tips can be found here. Please note: Savvas used to be Pearson and, while the name has changed, the products have not and the steps are the same.