No display after changing battery

Hi all,

So my Mums laptop decided to start playing up and the OS was reporting the battery as defective saying “Service Battery”.

Its a right pain in this Macbook 12 (as with many other Apple devices) because its 6 linked batteries all glued into the bottom case.

I decided to instead buy a used bottom case with a battery in it. Much easier, swap the logic board over, connect the whole thing up. Super.

I followed the guide here on iFixit for this replacement but obviously had less steps.

The only cable I didn’t detach from the logic board was the display cable as I didn’t need to. I carefully removed the logic board and placed it on the display still connected while I sorted the rest of the bits, then I put it all back together, connected the rest of the ribbon cables and tried to turn it on.

No display. Not even a backlight.

If I press power I got nothing initially, then I held it and nothing. So I assume the battery was flat. I plugged in the charger.

With the charger plugged in I eventually got the charging tone and then subsequently the start up tone when pressing the power.

However, nothing on the display at all. not even the backlight.

Checked the display cable but I had not removed or disturbed it and it still looked fine.

More checks and all looks fine but no display.

Put everything back to the original battery / bottom case but now the same issue with that one.

Disconnected the display cable fully. Checked it looks ok. Reconnected. Still no display.

Help please! :)

Images attached of it connected back with the old battery. Trackpad is disconnected in these photos so I could open wide enough for the photo.

UPDATE

Here’s the display connector. The little lock tab has come away at the one side because the tape was so stupidly strong but the cable still seems to seat nicely in the connector.