Trouble physically installing new lightning cable flex

I was so happy that I seem to have sorted out my constant rebooting every few minutes. I replaced the power flex and that didn't work, so I replaced the lighting flex cable and it has sorted it out. However, the connection has popped off. If you look at the photos its like the cable is a tiny bit long so the tension in the cable just flicks the connector up. Am I missing something obvious? It looks like its stuck down in the correct place as the lower connector is in fine. Any help would be much appreciated as I have never done this replacement before. :)

It's like the cable is slightly too stiff or something??!!