Video not importing even though import selected appear but then the footage is nowhere to be found

Is the media inside or outside the library?

Before even considering starting over (which of course would be something to try to avoid), it is worth experimenting in a new library, just to know if it would make any difference. Specifically: does importing to a new library even work now?

The answer will help us determine if the problem is with this one specific library or is something else.

Also: Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

This will help us look for possible issues, like third party bad actors who could be affecting FCP.

The files go wherever you assign. The default is into the library bundle. In library properties you can change the storage location to anywhere that you like, an assigned drive or a folder on the drive. FCP will put the media there in a folder called Final Cut Original Media. There will be similar folders for Final Cut Optimized Media, Final Cut Proxy Media, and Final Cut High Quality I think it says for render files, if you need to generate those. The folder structure is based on the event structure you have in the library. It’s really a good way to work with the media as it reflects the library structure, while still making the content accessible to other users and applications.

If you're new to FCP, you will save yourself lots of time with these two free tutorials:

Steve at Ripple Training, 60 minute FCP tutorial overview https://www.youtube.com/watch?v=HqUP7Zgeuck

Izzy Video tutorials. Slightly older so the UI looks different but the concepts are still correct. https://youtu.be/_jvyrnQpR1E?list=PLp5SAgbM8S87n1qvv34-PAU2zMHLlXyfb

So you're using the import window not dragging and dropping? Do not do what you're doing. Use the import window to import directly from the SD card. Do not drag .mts files off the card. FCP now does use them but the application works much better when the files are rewrapped to QuickTime, which it does when you import from the package on the SD card.

It is very easy to determine where files will end up.

Just select the location for your library. As you probably know, you can set the media location to be "in library" or you can choose a designated folder to store the media. In this case, you want the latter.

What I'd do in similar circumstances is to use an "import library" to import the media and store it in a desired location; then I can close this auxiliar library, or delete it altogether, and import normally to the working library using Leave in Place.

As Tom said, FCP will work much better with these files rewrapped as mov (which is what happens if you import them from the card directly).