No power to gameboy (original) with new batteries OR power adapter

Hello All,

I have recently had a itch to play my original Gameboy. But I when I went to play it there was no power going to the system. I have tried new batteries and a power adaptor to get power to the gameboy, but without any luck.

I have taken it apart to clean the battery connections, in case there is any corrosion, but they all seem to be in a reasonable condition.

Does anyone have any suggestions of what to try next? And are there any guides out there that may help me? I have googled searched, but many of the guides that I have found relate to corroded battery connections.