D.Opus no longer restores my last tabs on startup

In the past, each time I startup up Directory Opus it restored the tabs I had in place the last time I closed it. Sometime in the last few months, that stopped working. Now, every time I start it up, it gives me the exact same set of tabs. Every time. Regardless of whether I close some of those tabs prior to restart or open others.

Can you tell me what configuration item must be wrong? In preferences, it definitely is checked to "Open the listers that were open when the program was last closed".

I've attached my config file for reference.
[Config removed in case it has private data.]

You probably need to turn Preferences / Launching Opus / Default Lister / Update Default Lister automatically when closing a Lister back on.

If it wasn't turned off directly, it may have happened when using Settings > Set as Default Lister to explicitly save the current window as the default, if you chose the bottom checkbox:

Another relevant option is Preferences / Launching Opus / Startup / Open the Listers that were open when the program was last closed which you probably also want turned on.

(That one is more about when you restart the machine with windows still open and want them to be recreated after the reboot. But it can also affect things if you use File > Exit Directory Opus, or have Opus configured not to stay running in the background.)