If you use MapSource just plug in the Etrex do nothing to the GPS.

Start MapSource and tap on Transfer pick From device

When this window opens see screen shot do you see your device?????

b9T8Qxz

If you do not see your Etrex and you have tried Find Device the Try another cable....

If you can see your device then transfer your waypoints.

See screen shot


You should see something like this.

ErmuTyh

Try different cables and do not change any settings