I have had a PONO since the kickstarter, and it still works. Sometimes the USB connection to the computer works, and the computer recognizes the internal SD card, and sometimes does not, I would just retry plugging the PONO in again. I used this only to update the software on the internal SD card, and try to pamper the internal SD card, and not fill it up or erase my FLAC files. I think this is used also for any playlists. Make sure the cable is good. If the computer never recognizes it, you will be unable to update the software if it is older, but that may not be a bad thing, as it was one of the later updates that really slowed the PONO down in reading the cards.
I always take out the removable SD card from the PONO and put it in the computer in a SD card reader to download files from the computer to the card. I now have several 256 GB cards, one for my classical and one for my Rock and Jazz, as the memory can remember two cards, but not more, and it can take hours for the PONO to process a new card to show the library.