In trying to download and update all ads in a customer account, I noticed that particular ads don't download, even though all the other ads in the adgroup get downloaded.  I read that there have been in the past issues with ads that are removed or disabled, but in this case the ad is still active.  I also experienced a similar problem in the past with special ad types, but at least some of the missing ads are plain text ads.  Is there any other reason certain ads wouldn't be available?  Is there somewhere I can file a ticket in order to research my case?
Thanks in advance