An "unknown server" error occurs when you add or update articles in folios that aren't saved locally.
When you add or update articles in non-local folios, the Folio Builder panel shows the following error:
"The upload has failed. An unknown server error during processing. Please try again."
If still unsuccessful, use the next solution, or try using a workstation with more RAM, and more, faster, processors.
Separating the article conversion and uploading processes prevents the time-out issue described in the Additional Information section below.
When you import or update an article in a folio that is online, the Folio Builder panel initiates communication with the Publishing service. The source files are converted to the folio format and then upload it to the server. During the folio creation process, the service queries the panel to confirm that it is still responding. If the application fails to respond to the server queries, the service closes its connection with the panel (time-out), resulting in the "upload has failed" error.