Additional information: The device "Merrifield" does not show up on all of my PCs. One can only detect the USB serial port, but is unable to open a connection to the Edison. :(
Could you please tell me which Edison kit are you using? Have you tried using another USB cable, sometimes this can solve the issue. Other option would be to run the flashall method. You can find the instructions here https://communities.intel.com/message/311395. I suggest you to follow the instructions provided by CMata_Intel.