Chosen Solution
I recently replaced the LCD and digitizer on my Nintendo Switch and the screen wont turn on (black screen). What damage could of occurred if the battery was not disconnected prior to the replacement? Is there a way to test the LCD screen?
It may be possible that you shorted out the screen while connecting. Try restarting the device and charging it. If it still does not turn on make sure the device is turned off and see if there is any loose connections somewhere or the connector is not seated properly. Hope your problem gets solved and you dont need to replace again
