Delete key or dragging a file to Trash doesn't work

Question

I am new to Ubuntu and using Ubuntu 16.04 LTS. For some reason the Delete key or dragging a file to trash is not working. Pressing Delete key doesn't do anything. And dragging a file to the trash shows:

'filename' can't be put in the trash. Do you want to delete it immediately?"

I have already tried the solutions mentioned in:

• "Move to trash" not working
• 16.04 Delete key not working
• Can't move files to the trash

but they don't work.

P.S. I am able to use the delete key or dragging a file to Trash, under the root directory but on any other partition, the Delete key or dragging to trash doesn't work. However, Shift+Delete is working fine to delete files permanently.