Virtualmin backup to Rackspace failing with "HTTP/1.1 401 Unauthorized"

I have about 25 servers using Virtualmin backup to Rackpsace and all has been find for many years. About 2 weeks ago I started seeing failed backups to Rackspace. They are showing “Authentication at failed : Invalid HTTP response : HTTP/1.1 401 Unauthorized” in the logs.

I have reset the API key and tried everything I can think of but I just can’t get the backups to work any more. I plan to contact Rackspace for support too but I really know very little about what Virtualmin does so I expect I need to do more digging before I contact them.

Is there a good place to find detail logs about the API connection to Rackspace?