Owning a multimeter is absolutely imperative for doing this type of work. Trying to troubleshoot without one is just taking stabs in the dark; it will inform you of things you can not find out any other way. Once you get in the habit of using one regularly in your work (and learn to solder correctly), you will KNOW that your installs are going to work before you even test them, as opposed to HOPING your install is going to work, which is what I'm guessing you have been doing.
To expand upon the troubleshooting tips given above, you should be doing a continuity test from the nand points on the BOTTOM of the motherboard (corresponding to the nand points you have soldered), to the points on your JR Programmer where the harness wires plug in. By testing continuity in this manner you are testing from one end of the electrical connection to the other, if you don't get continuity, there is a break somewhere in the line. Apply this type of testing in all aspects of your solder work.
Also, test for shorts between adjacent points by doing continuity tests on NAND points next to each other. For this particular test, you do NOT want to be getting continuity.
Also, "Can Not Continue" errors generally indicate bad soldering/bad connections.
