Hi Jesus -
There is a bug in the 4.1.1 reviewer - the current version - where the app is not populating with MIBs that way. It will be fixed in the next update in about a week. But in the meantime, the workaround is for those people to just copy that dropbox URL from the email and paste it into the URL field in the Reviewer under User Settings. That will download the issue directly to their library.