GE side by side freezer

Hi,
Our freezer and fridge stopped cooling and there was frost on the back of the fridge. By reading the forums we figured that it was the mother board and the defrost heater.
We ordered the parts and replaced them. The fridge and freezer are now cooling but the coils have frost again and it seems to be building up. I don’t think the defrost heater P/N WR51X10101 is working. Could it be that we didn’t plug it back the right? even though it is very easy, we did replace a singe heater with a double one and had to cut the pink cable and use the extension cable in order to make it longer so it could reach the connector.
Any ideas would be greatly appreciate it!