The only difference I can think of is that the screen is no longer powered by USB (it was on a splitter that sent power to both the screen and the RPi3) and is instead powered from the 5V GPIO pins. I’d not expect that to make a difference because the screen is clearly powered correctly (in terms of powering up and showing the boot process) and because the RPi3 was constantly warning of undervolting using that splitter, while the RPi4 is powered through the DAC with a 40W power supply.
Just to be sure: can you ‘force’ a configure?
By toggling a switch of some setting (doesn’t matter what).
That fixed it! In fact the second I ran the configure I saw the extension appear in Roon. Post-reboot the display tab is now showing in the webUI. Thanks Harry! @spockfish
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I updated the guide to make this more clear (hopefully!).
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Call me cautious but normally if I add any hardware to an existing build I always reflash the latest build and resetup from scratch. I still find that this is the preferred way to do things.
Hey Harry, this same rpi3 endpoint is being a bit funny again. I’ve removed the dsi screen and put it on a different pi, but despite multiple reboots and reconfigures the rpi3 is still showing the display tab and is showing up in Roon as a display extension. Do I need to redeploy the image?
Maybe could have sent Harry a feedback before you kill(Ed) it but iirc adding a screen is detected by the s/w now but may be removal isn’t 
I didnt think of that (beyond the feedback here).
Too late now 
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