NRF_LOG is not working in my Custom Board


I am working NRF52840 as custom board, In my custom board NRF_LOG is not working I mean Nothing is displaying on terminal like tera term or termite. If load the code in Development Board (NRF52840 DK Boards) its working fine and also I Can view the data on terminal. My problem is in my custom board, can you please help me on this. How to solve this type of issues. 

Thanks & I am waiting for your response.