Canon PIXMA GM4040 Online Manual page 360

For details, see Setting an Encryption
With Encryption On, Cannot Communicate with Printer After
Changing Encryption Type at Wireless Router
If you change the encryption type for the printer and it subsequently cannot communicate with the
computer, make sure the encryption type for the computer and the wireless router matches the type set
for the printer.
Cannot Communicate with Printer After Enabling MAC/IP Address Filtering or Encryption Key on
Wireless Router
Key.
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