When you say it shows up, does it show up in Disk Management? If so, it’s possible that the drive was corrupted and the partition was damaged. Be careful about pulling the drives to test them. If you make any modification to them then the raid will have to be rebuilt; and if you need the data you will have to go to data recovery to retrieve it, if it can be retrieved. If you still have the drive “as is,” then you might consider getting some partition/data recovery software and see if you can rebuild the partition.