This could happen if you drag the connection vault to the very top of your screen and there isn't any space for the drop down on the right hand side to appear. However, if you pin the connection vault and then minimize the drop down on the right, you'll then be able to drag the connection vault. Once you're able to drag it, you can then pull it towards the left side of your screen and have access to the grips on the right and bottom right of the connection vault. Then you will be able to resize it.
Another option is to close Advance Steel and reopen it. This should give you access to the grips on the right and bottom-right of the connection vault as well.