external disk drive not showing up in Finder

Hey,

today I used my external disk drive to look at some old pictures. I ejected the disk and changed it to another one a few times but suddenly my drive doesn't show up in finder anymore. I can hear it vibrating, so I know it still works and it also shows up in disk utility but I can't select first aid or anything there.

My finder preferences also are selected to show external disks.

I clicked on eject in disk utility and it said that the cd can't be ejected because it's in use.

How can I get it to work again or at least get the cd out?:)