If my response doesn't help consider describing the setup and results for the experts to help you. For example, do you have multiple monitors and, if so, which monitor is to be recorded. Is any image recorded or just a black screen? How many tracks are created? (Should be two, or three if web cam is also being captured.) Right click the capture in the clip bin and select properties and provide that information; how much audio and video time is listed?
All that may be wasted effort or it may save you time when someone with real knowledge is able to help.
The following post, answered by kayakman, makes it seem impossible NOT to capture the screen on a PC when "Record" is used. One thing I have accidentally done is to use a very small custom area on one recording and forget to reset to full screen on the next.
However, on further investigation, I have discovered that it only presents for me when I am playing a blu-ray disc.
If I am using a standard application (excel or similar) playing a standard format DVD, or in a web application such as google maps, the recorder works very well. As soon as I am playing a blu ray - the screen captured is black and I only capture audio.
Is this a form of copy-protection?
In Windows 10, Camtasia Recorder's Preview Playback will playback the audio only. This was frustrating me for some time, thinking it was not recording the screen!! But it is! The image only shows up after you hit the "Save and Edit" button. You are then automatically redirected into Camtasia Studio 8, and there everything works fine. Ugh!!