You are right. The main plugin file is missing now!after finally open the zip file thanks to @NullMaster I just notice that the download-manager.zip file (the main plugin) it's not with the add ons or have another name now?
The zip only contains bunch of add-ons but now the main download-manager.zip file.
@abahnull really thanks for this update after a long time but please share the main plugin file too...........