Resolved this early yesterday AM .
1. ensure MIME types are installed and correct on server
2. compile application with BB JDE [make sure JDE version matches BB OS…]
3. Certify using keys from BB [i use protected API so need certification keys]
4. Isolate JAD / COD file. Rename COD to *.ZIP
5. Open and extract COD files from *.zip. DO NOT RENAME ANY FILES
6. Copy JAD [untouched] and COD files from ZIP to server in same folder
7. Send URL link for JAD file to BB via SMS or email
8. download and enjoy.
I was using a bog standard Linux server running Apache.
This worked for me. Hope it helps.