I agree. I was not satisfied with there tech support yesterday when I called and thats why I called again today. At least today I spoke with someone who knew a bit more then yesterdays tech support, but in the end she came to the same conclusion. That the seller of the software has to update there code so it will work with El Capitan. Tech support tried to download the same games and apps that I am having a problem with on there own computer at Apple, and they got the same error as I did "Download failed try again using the purchasing page"
So I think it could be a problem with the the App store itself, but that is not Apple's opinion. I think that when more people call in and complain, the more Apple support might listen and really try and fix this issue instead of putting the blame on the seller of the software instead of themselves and really try and fix the issue.