Apple Watch won’t charge or switch on

I changed the battery on my Apple Watch series 4 and followed the instructions on ifixit pages. Was very careful with all the ribbons etc but now it won’t charge or even turn on. Before the battery change I was at least getting the red snake which changed to green on charge but now I don’t even get that although the watch gets hot when on the charger so something is going in. Any answers would be much appreciated.