Nitrokey U2F on Arch Linux

I purchased the U2F key and deployed this udev policy (replacing plugdev with adm which my user is member of):

KERNEL=="hidraw*", SUBSYSTEM=="hidraw", MODE="0664", GROUP="adm", ATTRS{idVendor}=="2581", ATTRS{idProduct}=="f1d0"

I’ve rebooted to make sure the rule was properly applied. However both Google’s enrollment and Yubico’s test reports timeout once the key is inserted.

How can I get closer to why the enrollment times out? Any hints appreciated.