So your login password unlocks the keyring when you login; as only the
PAM stack actually has the password you entered. If it doesn't work it
is mostly likely that your distribution or packagers screwed this up.
This is true when using the Gnome desktop, but on other desktops it may not be. Specifically, on KDE this does not work (as has been discussed frequently) because KDE has its own " wallet" system independent of Gnome keyrings. The OP is using Mate, and although this is supposed to be "Gnome-like" the keyring support may be incomplete, I wouldn't know.
