If you are getting error “Server refused to allocate pty” while you are trying to login to your VPS then you are missing two device files tty and pty, you can contact your VPS Host or if you have Node access then you can correct problems by firing following commands from Node.

#vzctl exec VEID /sbin/MAKEDEV tty
#vzctl exec VEID /sbin/MAKEDEV pty

This problem generally occurs when udev gets updated.

Now you should be able to login into VPS