“Done” button greyed out on erase disk mode

I have put my mid-2011 MacBook Air into disk erase mode and the Macintosh HD is being deleted and the last message it gives me in te show details tab is that the “APFS Volume Macintosh HD on disk2s1 is ready for re-use” this seems like it is at the end of its erasing but the “Done” button is greyed out and it has been like this for an hour.