Yes, this is likely possible, but the problem is probably pre-flash. Many optical slave sensors fire on the first flash they see. Your Canon 60D pop-up flash may be sending a metering/communication pre-flash, so the softbox flash fires before the shutter is actually open. That would explain the beep and flash but no recorded light in the image.

A common fix is to set the camera’s built-in flash to manual output, if available, so it emits only a single flash during the exposure. If that works, the softbox slave should fire at the correct time. You may also want to block or diffuse the pop-up flash so it triggers the slave without adding much direct light to the photo.

If the 60D’s built-in flash cannot avoid pre-flash in your setup, then an optical slave may not work reliably from the pop-up flash alone. In that case, use a sync cord if the light supports it, or trigger the slave with a simple manual flash instead of the camera’s wireless flash control mode.