Optical viewfinder display went black

My Canon 6D status bar at the bottom of viewfinder display didn’t turn on. I cannot see ISO, shutter speed, etc insider the optical viewfinder. However, the 11 focus point sill turned on with ‘Red’ once in focus. I recently replaced the Shutter Curtain myself, hence, opening up the Canon 6D is fine for me. I would like to know where to look if I am going to open the 6D and fix this ViewFinder display issue?

Also, the WiFi is not working as well. Can I get the WiFi module from T6i and replace the 6D WiFi module?

Thanks!

Charles