WD External Hardisk can't be detected in mac

I have just bought external hardisk WD My Passport Ultra. It was well, however, it takes really long time to be detected on my macbook air. So I try to see whats the problem by using first aid in disk utility. It takes really long and I decided to stop it and then I unplug my hardisk. After that my macbook air can’t detect my hardisk any more. It is not appeared. Although it is already connected. I have tried to restart my mac again and again but still not working. What should I do?


It is possible the partition is corrupted.
Try formatting the drive.