The "Invalid Service Level" error occurs when a request is submitted with an invalid need-by date (e.g. a date in the past). Since the service level is calculated based on the need-by date, an invalid date prevents DocFind from calculating the appropriate service level.
The request appears as Idle / Check Manual with the error message in the audit screen.
To work on the request, action Request as usual and go to the Services tab to edit the need-by date and add the Service Level. In most cases, where the need-by date is within 4 days or more, the correct service level is "Normal-Local Search". If an item is needed sooner, use the "Priority-Local Search" service level instead.
Once you've added the service level, go back to the Main tab and change the Authorisation Status to "To be Authorised", and then Submit. This will re-run Docfind so that the proper default settings (like expiry days) are associated with the request, and so that locations can be added automatically to the rota if a match is found.