The most common reason for a .EU domain being quarantined is because it was not renewed and has been deleted. .EU domains have no renewal grace period. If not renewed, they will be deleted from your account 5 days prior to their expiration date. The quarantine period lasts for 40 days and any websites or email addresses attached to the domain names will no longer work. Once the quarantine period has passed, the domain names are released and can be registered by anyone on a first-come-first-served basis.

Can my .EU domain be reactivated once it's been placed in quarantine?

Yes, if the domain is still in quarantine, it can be restored. For 10 days after deletion, you may be able to restore the domain at the standard renewal price. After 10 days, the restore cost for .EU will be higher than a standard renewal.