I've played around with this for the last half an hour and, like you, I was unable to render the colour emoji's.
I re-downloaded the font file from google fonts, in case your copy was corrupt. No luck, still did not display.
I then changed to a different colour font file.
I tried this one...
https://github.com/adobe-fonts/emoji...jiOneColor.otf
And then also used Segoe UI Emoji from Windows.
Both of these worked, but not the noto colour file. No idea why that particular font file won't work.
I've attached my epub if you want to check it out.