I am finding that despite having completed the camera calibration step (all the laser related calibration steps, for that matter), the “Add Background” option remains disabled in Luban. The Laser module appears to otherwise be working fine, I am able to complete jobs.
I am connecting to my Artisan over WiFi, have also tried over the serial, same symptoms. When connected to Artisan, I see “Laser Camera” shows up amber (as does however the air purifier, which Luban is able to command just fine).
Maybe relevant,maybe not, the “automatic thickness measurement” also always fails:
… and the problem just magically disappeared with some combo of completing all the three calibration steps once more (as uneventfully as I had done before), and restarting Luban. Add Background works just fine now 
Just checking to see if you know what the issue was here. I’ve got the exact same problem (camera capture is not clickable) and it’s driving me crazy not being able to get my designs onto the actual material without just guessing where to place the material.
Well, tape a piece of paper onto the bed, laser your design on that, then position your material on top. The result will be way more accurate than using the camera.
Have you tried the apparent remedy that is above your post?
I’ve run through all the calibrations dozens of times at this point. Sometimes the laser will etch an entire square and other times only one or two of the lines. Also when I try to do the adjustment where I lower the laser to the bed and use the calibration card the laser won’t go lower than about 1/2 inch from the surface of the plate. I’ve never once been able to have it take any picture of the surface using the camera in the laser. I see lots of issues where some of the 9 pictures are messed up but mine doesn’t take a single picture and the Capture Image option in Luban has never once been able to be clicked. Remove background is able to be clicked but doesn’t actually do anything (since there is no background to remove I guess). At this point I’m loading a fresh copy of the firmware.
All around this software seems unbelievably buggy and the issues change daily without warning but maybe it’s just my learning curve at the moment.