RSS Feed Problems

Seem to have an issue with all Dassault RSS feeds. Have tried various feed readers such as Feedemon, Slack, Owl, Digg, Feedly to name a few. However, whenever you add a Dassault RSS feed they all report that they "don't look like a valid RSS/Atom feed". They all have the ability to cache user credentials and work with any other RSS feed that I try from multiple locations online. But NOT with the Dassault ones. What is so special about the Dassault feeds? and why are they not seen as standard by all these applications as this is a generic format used worldwide. Those feeds that do populate partial information never update after that point even when trying manually. This is also something that customers have commented on. Not everyone one wants to trawl through every single swym community one by one to see updates hence the purpose of RSS feeds. is it only me that sees this issue. If anyone has success with a feed reader please post its name and settings.