Not sure why it didn't work for you but I have IDrive setup under the Amazon S3 (compatible). Maybe it is your region your bucket is in? IDK. Anyways, as you can see from the screenshots below I have a drive connected.
There was a change at some point where when the service starts it reverts the the setting "CreateDrive_AllowCacheOnDrivePool (Default: "False") ". To get around this just set a deny write permission for the "System" user on the Settings.json file. This will prevent the System user from changing the file. Once I did that I was able to use a drivepool temporarily for my cache during my recovery process. As usual... do it at your own risk. It worked for me.