Michael was in Las Vegas recently and took some great time-lapse photos, but when he plugged in his SD card to his computer, the photos can't be seen. But he sees them on his camera. Leo says that Michael's camera can be connected via WiFi to his mobile device and he can send it that way if you see them in the DCIM. Was it Raw? Your computer may not be able to read it without a reader. It may also be that your SD card has failed, but the camera can see the thumbnails. Leo recommends using Recuva (Windows) and see if you can recover the files. If a Mac, there are other file recovery options. PhotoRec is a free and open-source option. Works for Mac.
The chatroom suggests connecting the camera to the USB of the computer and see if you can read them directly from the camera itself. Leo also recommends not using that SD card again.
If you're importing raw in Apple Photos, it won't import anything it can't read.