I get the following error text: Unknown Server Error (500). The following appears in the atlassian-jira.log: java.lang.IllegalArgumentException: Error parsing media type 'application/DBF Viewer 2000'
I have no idea why you are posting this question here. But this looks very the same: https://confluence.atlassian.com/jirakb/cannot-upload-dbf-files-to-jira-on-windows-333809711.html
This is caused by incorrect MIME handling by Windows when 'DBF Viewer 2000' is installed. The 'DBF Viewer 2000' program associates the .DBF file extension with 'application/DBF Viewer 2000' instead of 'application/octet-stream'. Remove 'DBF Viewer 2000' from the affected system. If you are still experiencing the issue I can suggest this program DBF Repair Toolbox https://www.repairtoolbox.com/dbfrepair.html