If you're on a Mac and are seeing this error, in some instances it will be due to a permissions issue and you need to allow full disk access to Steam. To do so, follow these instructions:
Go to System Settings
Select Privacy & Security
Select Full Disk Access, click the + and authenticate
Go to Applications, Steam, then click "Open"
Ensure the button is over to the right next to Steam in the apps list to indicate it allows full disk access
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Δεν ξέρω στα ελληνικά πως είναι, αλλά άμα είναι κάτι άλλο άνοιξε ένα ticket support: https://support.sega.com/hc/en-gb/requests/new?ticket_form_id=360003117678