As I had no better idea, I used the "Reset ZENworks Patch Management" option in Configuration > Security > Patch Server Configuration, at that (after running through the ZPM configuration again) at least had done the trick to get the DAU Bundles to show up in ZCC. Now testing if workstations will work too....

Good Troubleshooting.....

One if the first places I always look is to see if the DAU Bundle has run...And of course if it does not exist....that would be a huge reg flag.

Not sure why resetting was necessary, but how it operates is different enough and the policies different enough that starting from scratch is not a bad idea.

I have now verified that this indeed did the trick. Somehow, initially enabling ZPM on that server must not have worked. After all, enabling ZPM does a *lot*. Like actually creating and filling the ZPM folder with the necessary bundles and folders, which on this server hadn't happen.
Now, of course, I'm curious what processes are supposed to run when ZPM enables, and how to debug them. That resetting worked to fix it is nice, but it doesn't explain or help for the future knowing why and what had failed.

Reset just wipes all the ZPM tables and settings forcing you to start fresh.  If ZPM was upgraded from an old version, there is quite a bit internally that takes place to try and covert settings from the old to the new method.  Maybe the conversion was failing.  Due to how different things work, resetting is not a bad idea, though you may want a record of all old policy settings so you can try to replicate, though with differences in how things work this will never be exact

Well, that server/zone I was on never had the old ZPM activated. It *is* a Server with a bit of upgrade history, but ZPM is/was completely new on it.