Password not being recognised when installing updates and Plugins

At the top of my dashboard, its tells me that version 3.2.1 is now available, however when I try to download it, it asks me for my username and password…so I enter the username and password I use when i log into my dashboard, but it says my username or password is incorrect. I have changed the password, and my username is always the same, but it still never recognises it. It’s driving me crazy as I can’t install any plugins or do any updates whatsoever.