Resetting the ExpressKey Remote on Linux
You may occasionally find that you need to reset your ExpressKey Remote (EKR) to get it to work properly. These steps will reset the EKR and hopefully fix your problem.
Find the sysfs wacom_remote directory:
$ cd /sys
$ find . -iname *wacom*
There will be a line like the following: ./devices/pci0000:00/0000:00:14.0/usb3/3-4/3-4:1.0/0003:056A:0331.0001/wacom_remote
List that line:
$ ls ./devices/pci0000:00/0000:00:14.0/usb3/3-4/3-4:1.0/0003:056A:0331.0001/wacom_remote
The output will look like this:
Where 18437 is the serial number of your device.
Reset your remote by changing to your wacom_remote directory and issuing the following commands (example):
$ cd ./devices/pci0000:00/0000:00:14.0/usb3/3-4/3-4:1.0/0003:056A:0331.0001/wacom_remote
$ sudo su
$ echo '*' > unpair_remote
After that you'll have to repair your remote (see below).
Pairing the ExpressKey Remote
"How do I pair the ExpressKey Remote? 
The ExpressKey Remote comes pre-paired from the factory with an RF receiver. You can find it inside the left hand side compartment on the back. There is normally no need to remove the receiver although it can be used on any USB port. If your ExpressKey Remote loses its pairing you can re-pair by holding the ExpressKey Remote close to the left hand side of Cintiq 27QHD while holding “ON” the ExpressKey Remote power slider until the blue light at the bottom of the ExpressKey Remote begins to flash. Each Cintiq 27QHD receiver can have 5 ExpressKey Remotes paired at a time. Each ExpressKey Remote can only be paired with one Cintiq/receiver however. Using an ExpressKey Remote on a different Cintiq/receiver will require pairing."