Unit does not power up after repair

I replaced a rubber ABXY gasket in an attempt to fix the user complaint of ‘no XY function’ (the unit otherwise was functional). Using iFixit repair guides assisted me in the repair. After reassembling the unit, I turned on the power and the BLUE POWER LED flashed on for a second or two then went out, with the unit not powering on. Battery is charged with 3.72 VDC on the terminals. Went in a made sure all ribbon cables were seated and they appeared to be. That said, I suspect that one or more is not properly seated or I possibly damaged one. Are there any ‘gotchas’ that commonly happen when does a 3DS repair for the first time?