Nothing changed on mine, worked fine with Linnworks today, could it be a Linnworks bug update you haven't loaded? try closing Linworks and restarting...
That will put the code on every page, if you want to track conversions it should be in the box Configuration - Order - Conversion Code, then it will...
Basically you cannot export an order for a product from BP that does not exist in QB, so you need to have the SKU for the group the same in BP and QB...