I finally got Teensyduino installed. I had update Arduino to a compatible version.
Now I’ve got Teensy loader 1.44, Arduino 1.8.7. I’m using a Teensy 3.2 board. If I verify a Teensy Sketch in Arduino it launches Teensy Loader 1.44. If I try and upload the sketch I get:
No Teensy boards were found on any USB ports of your computer.
Please press the PROGRAM MODE BUTTON on your Teensy to upload your sketch.
An error occurred while uploading the sketch
The LED flashes when powering up the Teensy. Pressing the button stops the LED. The sketch will still not load.
If I load the hex file into loader, the program button is still disabled.
The docs seem to suggest that if the LED flashes, and stops when you press the button the USB cable is at fault. I tried two cables. I might have another to test with.