Remote Management Port 5900 Not Responding I am trying to understand why Remote Management (vnc) is not working on my iMac.  I enable Remote Sharing via GUI on Sharing "Remote Management."

when I request "telnet localhost 5900" I get an answer.  when I request "telnet 4-digit-ip 5900" I get no response.

Normally, I would think that my firewall is blocking it, but the firewall is off.

A portscan tells me that 22 (ssh) and 3283 (net assistant), as well as a couple of high ports (like Dropbox) are open, but nothing else.

I tried allowing access for everyone or just for me.  I have tried "Anyone may request permission" or not.  Are there other plist etc options that need to be switched on, that might have been accidentally turned off?
I did two things in sequence, which cleared up the problem.  First,

sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -activate -configure -access -on -users admin -privs -all -restart -agent -menu


Second, in the GUI, I turned off remote management and turned on screen sharing.  now port 5900 responded.  Next I turned off screen sharing again and turned on remote management.  Now it is still responding.

Probably a bug in macos...