The voltages look fine to me. It still sounds like a connector and most likely it will be on the Solenoid driver board. Can you remove the SD board and then check the solder side of the board for dry joints. You may need to reflow the connectors. Also, look around the relay mounted on this board.
You can also sand the connectors on the SD board and check the pins (as described earlier)
Another quick check would be the fuse under the playfield. If this has blown, the game will go into attract mode but not kick out the first ball.
The power on MPU flicker does not count as one of the seven flashes. There's the little flicker, one flash, a pause, then 6 flashes until the game boots and the led is dimly lit. The game should then go into attract mode.
