Hi, Sandra.
I believe you've already had the very similar problem (also manifested by " Error decoding authentication request message" error), here is the ticket: [https://support.gluu.org/integrations/profilesaml2-2498](https://support.gluu.org/integrations/profilesaml2-2498)
Was it the same issue? Did you follow advices I gave you? If it's a different issue, please read my last message in the ticket I referenced again and try to provide a little more details (log records, description of your setup etc)