My best guess is that cupsd.exe is not running and that a(some) support file(s) is(are) missing.
That would be my best guess too, but it is possible that the current version in netlabs-rel, is not the same as what ArcaOS is installing. According to ANPM, it is cups 2.1.3-7 i686 version, with:
cups filters-libs 2.1.3-7
I also have the hplip stuff, which you may not need. There are probably other things involved, which is why you should use ANPM (RPM/YUM) to install it..
How is cupsd.exe started on a working rpm-cups system? - Just wondering if there is any special incantation required.
It is the same as before:
Path and file name: CMD.EXE
Parameters: /c detach cupsd.exe
in the STARTUP folder.
Try this: go to a command line, and type "PKILL CUPSD" (without the quotes). If it is running, it will kill it, and tell you so (you need to do that 4 times to completely kill it). When it is dead, PKILL will say that it failed to find CUPSD. If CUPSD is already running, detached, and you try to start it from the command line, it will just terminate, with no messages (which seems to be what you are seeing). If CUPSD is running, you should be able to open your browser, and go to web page: localhost:631 and the CUPS home page should open (but you know that part).
So, first, lets Pkill CUPSD, to see if it is, or is not, running. Once it is dead, try starting it from a command line (no paths should be needed), without using detach. Then, you should be able to see what it is doing. It will simply start, and nothing more will happen, if it is running.
One other thought: Do you have a firewall that is blocking it?