Unable to perform backup - greyed out and says I have no files

I have a WD My Passport Essential, had it for quite a few years, it hasn’t come to any physical damage at all, but suddenly, when I plug it in to my laptop, it doesn’t let me backup my files onto it. I’ve attached a screenshot. The bars are just grey and it says I have no files to backup, and no files backed up.
Can someone help please? I haven’t backed up for a long time and really need to do it!

Many thanks
Sophie

Is your WD Passport detected within Windows Explorer as a regular external hard drive in the Computer section? Does it allow you to manually copy/paste your files into it?