I can't turn off my computer

Hi!
Coud any body help me?
I can’t turn off my computer, when I click un turn off, appears the ubuntu mate’s logo, but, The computer doesn’t turn off.
How can I fix it?
Thanks you, and, if I make a mistake writing, sorry, I’m learning english XD

Which version of Ubuntu MATE are you using?

I’m using ubuntu mate 15.10

Press ESC when you see the logo. Some details will appear, which can give an indication of what’s happening.

If you boot your system without the quiet and splash flags, then this screen will be very verbose with the start-up/shutdown details.

In my experience, I had a system take up to 3 minutes to shut down since it was waiting for a service to stop.

I think that some process does not quit while it is shutting down . Or maybe your ram is little . I had hp compaq 6510b . Used 64 bit UM and my swap and ram did not clean on apps close . The machine either turned off realy slow or it did not shutdown.