Sideacar issues - Displays

I have set up my iPad and Macbook pro for sidecar however, when i have my ipad on the left side and my macbook on the right. i cannot use my mouse to drag an item from my macbook onto the ipad (left to right.) instead i have to figure out what side of my macbook display is moving onto the ipad display. i am wondering whether this is a setting issue i can change myself of i have to put my macbook on the left and my ipad on the right.