Importing from tape based cameras can be problematic, so there are no guarantees. You just have to keep fiddling. Your camera's user manual should have instructions on how to export and what cables to use. You Tube often has good tutorial videos, so you might try doing a You Tube search. Below I have provided a couple of other links.
Did you try using the Image Capture app in your Mac's applications folder? Try and see if it recognizes your camera.
Sometimes a bad cable, adapter, or socket can prevent recognition. That's mostly the problem that is reported on this forum. You might consider changing our your cables to find out, and trying a different socket. What cables and computer model are you using? You should be using fire wire cable and whatever adapters are necessary to connect it to your computer if your computer does not have a fire wire socket.
Sometimes starting the camera running and/or starting the camera recording can trigger recognition.
To cover the bases, here is an Apple help link that reviews the procedure for importing from a tape based camera:
https://help.apple.com/imovie/mac/10.1/#/mov6af9c94c1
And here's another help link that discusses cables:
https://help.apple.com/imovie/mac/10.1/#/mov50a336efa
Hopefully you will be able to import from your camera. There are many reports on this forum of difficulties in importing from tape based cameras. If you have an older pre-iMovie 10 version that still works on your computer, you might try importing into the older version. There has been some success with that procedure. Also, you can try importing into the QuickTimePlayer app on your computer. It can be frustrating, but there is nothing to do but keep trying things.
-- Rich
