An access point (wireless router) can be configured with as many as four WEP keys. Only one key is used on the network at a time, however. The keys are numbered, and the number of a key is referred to as its key index. All devices on the wireless network must be configured to use the same key index when multiple WEP keys are configured on the access point.
Select the same key index on your printer as you are using on your access point.