New SSD & RAM - unit won't power up

I replaced the HDD with a SSD and upgraded the stock RAM with 2 @ 8GB modules from iFixit. After reassembling, I would get the chime but screen was black. Checked the power / data cables to the screen - all was well. Opened the unit back up to check all the connections including that the new RAM was properly seated. When I buttoned back up, no chime. The first LED is solid green when connected to power, but the second LED blinks and the fan does a brief “twitch” when it blinks. I had googled to see if there were any easy things to check - most said recheck the ram was seated well, so I undid the machine and checked it again. Still no dice. I was careful not to touch the connections on the power supply board. Any advice?