Retrospect "Waiting for Media" backing up to ReadyNAS

I've been using Retrospect on my Windows PC for years.  I'm currently at Retrospect 10.5 on Win10 x64.

I recently bought my 3rd ReadyNAS, with all three in service.  (An NV+, an Ultra 4, and now a 214.)

I moved the destination for one of my disk backups to go to the new 214.

It works fine if I run Retrospect interactively.

But, if I set Retrospect to run automated at a specific time, it sends me an alert email that says ,"Waiting for media".

Note that it works fine backing up to the Ultra 4, in either automated or interactive mode.  (I have three different backup scripts for three different drives.  The other two drives back up to the Ultra 4, and work fine in the automated mode.)

When it's waiting for media, I have to kill Retrospect, relaunch it interactively, and it works perfectly in the interactive mode.

My share on the ReadyNAS is configured for Anonymous users to have full read/write access.

File access is set up for guest to have read/write access.  I started with a clean, empty 214.

I have Retrospect configured to "Run Retrospect as the logged-in user", which is me.

Except that this works fine on the Ultra 4, I would suspect it's a problem with Retrospect permissions.

But, because it works on the Ultra 4, I suspect I'm missing some permission configuration on the 214.

The Ultra 4 configuration differs substantially from the 214 configuration, so I can't tell what I might be missing.

Any advice for how to fix this, or how to diagnose this further?

Thanks in advance.