I’d rather cancel (delete) previous printout jobs by erasing pending jobs over built-in buttons. Meaning that you need to erase/cancel already present buffer (its memory with files, pending jobs) within this printer memory chip, on Canon MG2500 itself (even just powering-off might not help). Cannot confirm or think of any other workaround option. Once this current file erased (over printer buttons) you can repeat things to “see” if able to cancel current print jobs by mouse click as well, reproduce things. Software communication with your printer is there, hope things will work as expected.