Problems with udev rules

Hello,

I'm using the udev rules from here .
However, the group of /dev/ttyACM0 is not changed to pludev neither are the permissions changed.

udevadm test /dev/ttyACM0 gives the following:

[root@herrod ~]# udevadm test /dev/ttyACM0 
calling: test
version 231
This program is for debugging only, it does not run any program
specified by a RUN key. It may show incorrect results, because
some values may be different, or not available at a simulation run.

=== trie on-disk ===
tool version:          231
file size:         7291171 bytes
header size             80 bytes
strings            1819099 bytes
nodes              5471992 bytes
Load module index
Found container virtualization none
timestamp of '/etc/systemd/network' changed
timestamp of '/usr/lib/systemd/network' changed
Parsed configuration file /usr/lib/systemd/network/99-default.link­
Created link configuration context.
timestamp of '/etc/udev/rules.d' changed
timestamp of '/usr/lib/udev/rules.d' changed
Reading rules file: /usr/lib/udev/rules.d/40-usb-media-playe­rs.rules
Reading rules file: /etc/udev/rules.d/45-espruino.rules
Reading rules file: /usr/lib/udev/rules.d/49-sane.rules
rules contain 393216 bytes tokens (32768 * 12 bytes), 32238 bytes strings
25863 strings (208413 bytes), 22554 de-duplicated (179485 bytes), 3310 trie nodes used
unable to open device '/sys/dev/ttyACM0'
Unload module index
Unloaded link configuration context.

I'm using Arch Linux.
Any idea why the group is not set?