Do you have another Pi?
The support for Pi Zero W wasn’t part of the OS when the image was built back in Nov 16’ so you may be able to install the emonSD to another Pi and do a full apt-get update and apt-get dist-upgrade to get the latest kernel and files required by the Zero W. The advantage of doing it this way is that you can set up wifi on the other Pi before transferring the SD card to the Zero W as it has no Ethernet to configure WiFi the “emoncms” way and I do not know
Alternatively you can build the image from scratch on the Zero W following this info
When starting with a blank Raspbian image remember to add a blank
ssh file and a
wpa_supplicant.conf file containing your WiFi SSID and PSK settings in the boot partition before moving it to the Pi Zero W. that way you won’t need to attach a screen and keyboard.
Let us know how you get on.