Do Help > Log Files > Show Log Files.
Sort the window by date. Open the latest log. Check and make sure it has lines that indicate "streaming start" or "start recording". If it's not there, try starting and then stopping a new session. Let it run long enough that you can observe the problem you're trying to troubleshoot, then look at the logs again.
For instance, your first log *did* have a session in it, but it lasted less than two seconds. OBS reported the number of frames output as fewer than rendered but doesn't say why. I think you might need a longer attempt. That said, window capture is the least performant method. Display would be better. I don't think syphon works on WoW.
14:08:53.721: ==== Streaming Start ===============================================
14:08:55.287: [ffmpeg muxer: 'simple_file_output'] Output of file '/Users/zach/Movies/2018-04-10 14-08-52.mp4' stopped
14:08:55.287: Output 'simple_file_output': stopping
14:08:55.287: Output 'simple_file_output': Total frames output: 61
14:08:55.287: Output 'simple_file_output': Total drawn frames: 83
14:08:55.301: ==== Recording Stop ================================================