Error reporting when starting the document

When I open a document and encounter the following error, how can I resolve it?
The document could not be saved.Please check connection settings or contract your administrator.When you click the ‘OK’ button,you will be prompted to download the document.
Download failed.
Press “OK” to return to document list.

Hello @yuanli201009

Please specify where do you see these errors. It is in integrated test example or in any DMS?
Additionally, please provide version of Document Server and installation type (Docker, DEB/RPM).