A. The user does not have permission to upload an asset with the specific file extension

B. The file extension is not registered as an allowed asset MIMES in the OSGI config Day CQ DAM Asset Upload Restriction.

C. The MIME Type mapping setup for the file extension does not exist in OSGI config. Day CQ Scene7 Asset Mime type Service.

D. The file extension is case-sensitive and should be all lower case.