In the event that technical issues or scheduled maintenance renders Royal Mail's OBA system unavailable, the simplest course of action is to wait and generate your manifest after the OBA Is back online. If you cannot wait and need to manifest immediately, you can create an emergency manifest on the Royal Mail Emergency Manifest page.
Important Note to Prevent Double Billing
You should only create an emergency manifest if the OBA system is unavailable. Furthermore, if you create an emergency manifest, the next time you successfully manifest in Shiptheory, those shipments you manifested on the emergency manifest will be sent to Royal Mail, potentially resulting in double billing. To prevent this, ensure you cancel any Royal Mail shipments in Shiptheory after you have created your emergency manifest. Alternatively, if you have too many shipments than is convenient to cancel manually, contact your account manager at Royal Mail and ask them to remove any duplicate charges.