Not recognising WD 3 TB USB Drive (sometimes)

Hi I have a WD My passport 3 TB drive I have been using for backups. I am having issues with it, sometimes I can plug it in, as I did last night, all files and folders showing and I used macrium reflect and did a backup of my data. However I look at it this morning and first it shows the drive but shows it as empty, nothing in it, but it is not because I have had this happen before. Then...