1) If it was NOT working before the battery swap, there could be other issues. But for now, let's say that the original battery WAS going bad, and changing it most likely did NOT cause this issue.
2), 3), & 4) Did you use the following video guide - as a reference when you changed the battery?
If not, you may want to use it to disassemble the device again, except this time taking NOTE of where the POWER SWITCH is (on the control board that is removed to get to the battery connector).
So what I would do now is take the unit apart again, and this time double-check ALL the connections, especially the battery connector and that it is FULL seated in the connector.
Then, while the case us still open, try to press the power button ON the CONTROL BOARD, to see if the device will come on - and stay on.
This is because MOST batteries you purchase do have a little bit of charge, usually enough to at least power up the device.
Also, you may notice (from the video) that the power switch actually sits UNDER the "button" in the frame, and it COULD be mis-aligned enough so that pushing the button does not actually push the switch.
Does that all make sense?
If so, please look at the video a few times, and then CAREFULLY open the device up again and double-check ALL the connections and TEST - using the actual power switch by GENTLY pushing it (don't knock it off the control board - that would be bad).
Please let me know what you find - when you can.
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