Having a problem deleting Time Machine Back Ups

I recently bought a new Macbook Pro and I connect my Time Machine external hard drive and when I enter time machine, my computer says "Can't connect to a current Time Machine drive". I am able to access the back ups through finder. When I put one of the back ups into the trash. Now the trash will not delete the back up because it says that it's in use (which it's not) and when I try to put it back into the original folder it doesn't allow it. However when I disconnect the hard drive the backup disappears from the trash can but when reconnected the folder shows up again in my trash. So PLEASE does anyone know:

1. How do I fix the problem of the folder reappearing in my trash?

2. If my macbook can't connect to my hard drive, how am I supposed to delete my previous back ups sinnce drag and drop is clearly not the way?