First, try checking the battery covers on each device to make sure that they are fully tightened. If they are a bit loose, that can cause some binding around the trackpad area. Second, check to make sure that the tray is free of debris - you can rub it with a barely damp cloth to make sure.  Lastly, install the keyboard first, making sure that the device fits underneath the lower lip before you snap in the top. Then install the trackpad the same way. If you continue to have trouble, submit a ticket by clicking below.