Maybe a dumb question but did you strip the wires before twisting them together?
I would beg, borrow, or steal a multimeter so you can actually troubleshoot the issue. Start by checking continuity and resistance through your green test connector switch and wiring extensions. Then check continuity through your "twisted" wires. I don't have the 16bit ecu pinout but they're floating around. If your wiring mods are as they should be (which I suspect is not the case) start moving down the harness until you find the issue.
If you grab some piercing leads you can essentially isolate the wiring you've done and check the connections that you've made. You won't find a faulty connection by checking at your splice unless there is a problem at your switch.
It's possible you have a bad connection where you extended the test connectors to the switch and/or your connections to the switch are faulty. It's also possible you pulled on the harness too much and damaged it elsewhere.
Of course there is always the possibility that lightning has struck your car's test harness leaving it a smoldering pile of goo behind the dash. If this is the case see aforementioned multimeter statement.
The problem with just randomly "fixing" things without actually knowing the cause is that a faulty connection may work sometimes but it really ruins your day when it decides to stop in the middle of a reflash.
disclaimer: I'm not encouraging anyone to actually steal anything, it's a figure of speech.