Royal Mail requires manifest to be submitted at the end of the day if any labels were printed this day. If manifest will not be filed this is the error message will appear when you print Royal Mail labels:

Error: Cannot generate labels. You haven't submitted Royal Mail OBA manifest in the last 24 hours. Royal Mail requires manifest to be submitted daily. Go to Royal Mail manifest and file it. 

To avoid this error please make sure to file the manifest at the end of each day after you printed Royal Mail labels. In case you got this error, the easiest way to resolve it would be to file the manifest with your current consignments. If there is still a problem please contact Linnworks support to resolve the issue.