My Passport 2T is totally full and the Macbook cannot recognise it

While I was backing up my data from my mobile phone to My Passport 2T portable hard disk, My Passport 2T became totally full. Then, my Macbook has not been able to recognise My Passport 2T Drive. What can I do to make the Macbook recognise it again?
How can I remove some of the files? Thank you very much.

Hello, YY131

Well, follow the instructions mention on the link below in order to isolate the issue.