Available space not showing on 2TB My Passport

I have a WD My Passport 2TB which recently ran out of space. Now I have been deleting files I no longer need but my available space is not changing. I’ve deleted over 40GB of data but I still can’t transfer my new files over because it says I have only 280MB of space available. I checked and these files are no longer on my passport. 

How do i fix this? Please help!

Check if the space is being reserved by the recycle bin. If that is the case, to delete the files just empty the recycle bin.