Struggling with something that probably shouldn't be giving me as much trouble.
I want to connect the development NPM server to my Duet3.

I did the usual git fun, and made a local branch for DWC, made a simple change (building a laser... I don't have a Z axis! just xy), and then did:

npm install 
npm run serve

From there, I can load it in Chrome.

But clicking the connect button...

I have tried connecting using both duet3.local, and the IP address I normally use to access Duet Web Control.

I have a Duet3 running with a raspberry pi 4 in SBC mode.
version numbers:
Board: Duet 3 MB6HC (MB6HC)
DSF Version: 3.3.0
Firmware: RepRapFirmware for Duet 3 MB6HC 3.3 (2021-06-15)
Duet Web Control 3.3.0

Also, when I added "M586 C"*", it reports the following error:
M552: Network-related commands are not supported when using an attached Single Board Computer

Are there any additional steps I needed to take? Any steps because I have an SBC installation?

Thanks in advance!