These devices use the MAC address, not a pairing code.
The Router Limits RL-100, RL-150 and RL-160 require you to input the router's ID/MAC address. The ID/MAC is on the bottom of your router. Enter it as numbers and all capital letters.
A MAC Address has this format "xx:xx:xx:xx:xx:xx". Valid characters are only in the range of 0-9 (numbers) and A-F (letters). Look at the MAC Address carefully, it can be easy to read it incorrectly. For example, the number 8 can be mistaken for the letter B.
Visit the automatic activation portal and select "Pair Manually".
Upon your first login at routerlimits.com you will be asked to set the network name (WiFi Name/SSID) and password (key). That is what you will use to actually connect to the WiFi. You can change the name and password at any time on the settings page in your Router Limits account.
Note: The default WiFi name and password is "Router Limits" and the 12 digit Router ID/MAC address you used to activate the router (on the bottom of your router).