L14 ?
How close is that to an L12 ?
With L12 on the operator's console there will be a panel that displays the
manual mount requests...
will list the volser, its slot, & drive on which to mount it...
with 3590B1A drives, they will also flash the volser to be mounted...

Now when you first go into manual mode, in the panel/window within which you
will see your mount requests, there is a bunch of JUNK TEXT to read and then
hit PF12 to "cancel" out of the text and get to the window where you need to
be to do your tape mounts... could this be the case ? ? ? need to hit F12 ?

Dwight