Ummm, not a lot of information here for us to go on. Like computer platform (Win? Mac?) for a start. But, just a few general guesses/suggestions: First, in the camera's menu's there might be a selection about HOW the camera is connected to the computer: is it set up as a drive? Or a mass storage device? Or a PTP? On my Nikon,s it has to be set up as a PTP for it to be seen for downloading/transferring to the computer.
On "some" systems, the computer has to be powered on AND connected BEFORE the software is opened, so there can be some "procedural" hoops that must be jumped through for camera-to-computer transfers to go right.