The Steam Packet says it may be 48 hours before its website is fully working again.
Users have experienced problems today, being unable to access the site or make bookings online.
The company says it is the result of a third party website hosting and administration issue, over which it has no control.
The problem was rectified yesterday by third party providers, but the Steam Packet has been told it may take up to 48 hours for the repairs to work their way through to the various internet service providers.