Start with the right checks.
Files On Demand saves local storage, but an online only file needs a connection to download. Plan around the files needed for the next task.
What to do next.
Connect to the intended OneDrive account and a reliable network.
Locate the needed files in the OneDrive folder.
Use Always keep on this device for the selected files when appropriate, following Microsoft’s current guidance.
Wait for downloads to complete and check available local storage.
Check the result.
Disconnect only when safe and open a harmless sample offline. Keep the cloud account and local availability distinction clear.
Stop and get help if…
A file does not download, the account has an error or business policy controls local copies. Do not move shared folders out of OneDrive to work around the issue.