A Microsoft file hosting and synchronization service.
Hello,
May I know where you are trying to access the files from, such as File Explorer, Microsoft 365, or OneDrive online?
Also, is the OneDrive icon visible in the Windows notification area?
Right-click the OneDrive icon the taskbar, and go to Settings > Accounts.
If you have already signed in, click "Unlink this PC".
Once done, you will be asked to sign in to OneDrive.
Re-link your Microsoft account again.
If you are still having issues, try resetting OneDrive by following the steps here-