The heartbeat LED on the B426 is off.
No communication failure, trouble or communication module missing error messages at the keypad.
Check the TMPR pins next to the Ethernet port on the B426.
Remove the jumper from the pins; the B426s heartbeat LED will start flashing to show the firmware version on the board and then it will resume normal or trouble operation depending on the condition on the B426.
When the Tamper jumper is covering both pins the heartbeat LED is turned off to save power.
When the B420 or B426 has been programmed through the web interface and the setting; Panel Programming Enable has been set to NO, the B420 or B426 Ethernet Communicator module programming screen will look as displayed below with programming parameters not available for changing.
The card will need to be accessed again through the web interface and Panel Programming Enable must be changed to read YES.
Log into the Web-Browser and select Maintenance. Click on the drop-down arrow beside the field; Panel Programming Enable and change it to Yes.
When programming the B420 or B426 to be connected to a GV3 or older panel the web interface is used.
When programming the B420 or B426 to be connected to a GV4 panel, use keypad programming.