Hello & Welcome to Just Answer,
Sorry to hear of any issue you are having with your device.
To help you with this issue, may I ask:
1) Was the unit working AT ALL - before the battery was replaced?
2) WHERE was the battery acquired?
3) Did you attempt to power up or otherwise TEST the unit - AS the battery was being replaced?
4) Did you have ANY difficulty during the battery replacement, especially when putting the main control board back in?
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.
If this has answered your question(s), please take a moment to rate MY service level (Excellent is my goal) so that I get credit for helping you with this question.You should see some "stars" to do that, but please let me know if you do NOT see them (you may have to scroll UP or DOWN) or can not use them.
Thanks, ***** *****--. .-(im)
I see it has been a few days and I just wanted to follow up to see if you have any more questions concerning this issue or if the issue was resolved?
I look forward to any further questions or results that you may have.