It might be an issue with how the mouse buttons are kind of buggy sometimes, the previous version of the game had issue like that with keyboard buttons. Maybe try refreshing the page?
i did actually, when i commented that i had tried multiple times but also i think its just that my middle click button doesnt have the job of the middle click and if you want to further look into that, my laptop is a MX10 i think, if you search for that and it comes up with a laptop that has a middle button between the left and right click that has blue dots on it, thats the one.