How to start Unity while completely off line?

I work in an environment where all my development is offline. I recently had my SA install Unity 5.6.1f1 on my offline dev box via the large install exe (not the installer). However, when I start up Unity, it asks me to sign in to my Unity account. This fails because this box is not online. So my question is, how do I get around this? I am required to do my development on this box and this box is never to touch the internet.

You don’t need to log in, in order to use unity. You can use unity without login in and without internet.