First, quit Arduino. The following is just a test to see if Teensy communicates, so fully quit Arduino for this test. You don't need Arduino for the test and it just makes everything more complicated for the case of a simple hardware test.
Then
turn off Auto mode in Teensy Loader (the 4th button in the toolbar). It should look like this when Auto mode is off:
Then press the button on your Teensy. If the Teensy and your USB work, you should see this:
If there's no response, Teensy Loader doesn't change, then something is wrong with your USB or the Teensy is dead.
USB charge-only cables sold for cell phones are the most common problem when Teensy's LED blinks but there's never a response on your PC. Those cables have only the 2 wires for power but they lack the 2 wires for data.