Is the folder you are trying to delete one you created, or a collaboration folder you accepted an invite to.
To Archive a folder you own choose Archive. Then from the Archive you can Permanently Delete the folder.
If it is a folder you accepted an invitation to then you need to choose Leave Folder.
If neither of these are working then we will work to resolve the problem. Please either reply with the name of the folder or send it to me in a Private Message.