Are you using Windows? Does your PC normally make a chime sound when a USB device is plugged or unplugged?
Even if Teensy is blank (they are all supposed to ship with a LED blink program which shows up as RawHID) you should get a HID device (not serial, no COM port) after pressing the pushbutton (and the orange LED blinking should stop).
I have a similar problem, and this thread helped fix it. I'm using windows7 x64, Teensy3.2. I have programmed several successfully, then suddenly had trouble. When I plugged it in, blink runs, and I see it has a port "hid#vid_16...(Teensy3.2)".. assigned. I click upload, then it stops working. Next time I try, it no longer has a port. I can't load anything, and it does not run blink or anything else. I managed to break two of them before finding this thread, and followed Kurt's method. I realized I had not pressed the button, and did not see it referenced as USB serial port, just the HID generic port. With a new teensy, compile blink, pressing the button assigns a USB serial com port (COM38 Serial) , and I can program it without problems. I found that just plugging it in and pressing the button does not work, I have to compile first and wait for the Reboot window to open.
So Paul, it would be a great help if you could spell out a few details of what is happening here, why does pushing the button not start the USB serial driver if the Reboot window is not open?
How one should "normally" proceed in the first few steps to reliably start uploading, assuming a good cable and proper drivers are loaded? I see different results depending on the sequence of actions, starting the IDE before/after plugging in, etc. I have not found a simple set of instructions to start this correctly, just explanations for when things go wrong.
Also, I now have two teensy3.2 that don't work, can't be programmed, nothing broken but somehow I need to get back to the HID#vid port or reboot to serial com port. How to proceed?