Arduino port not detecting

Hi my arduino mega was working fine, i needed to alter the program and now i cant upload anything as it doesnt seem to be connected, there is opower there and the current program on the board still runs. If i swicth boards to my UNO it comes up no problem on com3 so the cable is fine.

Any suggestions

Could you pls repeat your question incl. a more precise and structured information about your given situation?
I couldn't follow your English.