The machine will only see two instances of "%": one to start and one to end. So if you have your communications software set up to add a % to the start of transmit and also have a "%" written into the first line of your program, you'll get nothing transmitted.
If it is too difficult to find your comm settings start lines, then try deleting the first "%" from your program and then try the transmission again.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)