I recommend using another USB cable and making sure the drive is plugged in directly into a wall outlet. If you still have the issue then it means the partition is corrupted. You should be able to use the drive again if you format it. Formatting the drive will delete all data stored on it. Before formatting, it may be possible to still extract the data utilizing data recovery software.There are several kinds of Data Recovery software available. If you do a web search for Data Recovery it will yield plenty of data recovery software options.