Tape Library. How?

Question

System administration

Comrades, I need help with a tape library. A thousand years did not work with this, and forgot everything. From what I remember, there is nothing close to the reality that I see.
And so the essence:
Given:

1. Server with Windows 2012 R2
   
2. HP MSL-2024 Tape Library
   

Screenshot 1

The library is connected to the server via SAS via the HP Smart Array P212
controller Backup software - Backup Exec 2014 (and even more recent versions)
In the device manager it is defined as follows:

Screenshot 2

In Backup Exec:

Screenshot 3

The first thing that annoys is that only 2 cassettes of 781 GB are displayed in the library cells. (although everything is crammed to the eyeballs - 24 pcs.)
2nd - with backup, in theory, it should be like this: the cassette is filled, the next one is served, etc. Well, that's how I remember it, when I worked with them.
Now, 2 cassettes are clogged and there is a request for fresh ones. But it shouldn't be the same. It's not a streamer...

Another screenshot:

The driver seems to be all fresh. Supported controller (according to specification). The only thing is that the firmware of the library is old, but there is no way to update it, since in order to download it, you
need an HP service contract. And he, behind the prescription of years and the change of several generations of admins, is "loved". But something I do not think that this can affect the work ...
I've been fighting with this for a week now, and I can't do anything. Maybe someone will have any thoughts? It can even be crazy :) (well, except for

Answer 1

> what is annoying is that only 2 cassettes of 781 GB are displayed in the library cells. (although everything is crammed to the eyeballs - 24 pcs.)
You need to start with this. It is possible that inside the device is dirty and the codes from the cassettes are not readable.
Here is a video , the truth about dell. The author is on Habré - @fagear