There is an ongoing thread here: https://www.flyertalk.com/forum/radi...rtificate.html

I'll ask the Radisson mods to merge.

My investigations have shown that "unable to redeem" has meant that we've used the certificates elsewhere and they stay on the Ecert page as unused. I spent an hour or more on the phone getting to the bottom of my unusable Ecerts, and, it turns out, they'd been used already. It's hard to track, and appears inconsistent-- sometimes they disappear after being used, sometimes they don't.