I encountered the same situation tonight. I created an empty session in 7.0.4 and imported one mp3 audio file. I hit the F3 button to view MixConsole 1 and though Racks were enabled, they were not there. I then disabled them, saw a slightly different look to the mix console, but after re-enabling them, it was just like before, they were not there. I then tried viewing MixConsole 2. When I enabled the Racks there, I could see a very small section appear, I was able to drag it out and expand it so that I could then see the Racks. I've attached a couple screenshots as well.
I've got some templates that I created in an earlier version of 7 that will allow me to "get my work done" but I have noticed that when I open some of my sessions created in 6.5 that the MixConsole 1 and/or MixConsole 2 has issues displaying "properly." For the most part, MixConsole 1 works fine for me if I use a template when creating a new session, which I do 99.99% of the time, but in this particular instance, I was just doing some touch up on an audio file and didn't need a full-blown template. Overall, I'm happy with 7, but even with the 7.0.4 update I'm finding that the MixConsole is still a bit buggy and not nearly as solid as I'd like for it to be. Hopefully this will get resolved soon
Steps to re-create problem:
1. Create empty project
2. Import an mp3 audio file
3. Hit F3 to view MixConsole 1
4. Mixer displays very large tracks with no Racks even though Racks say they are enabled
My system specs are in my signature and this is for the 64-bit version of 7.0.4. I don't have the 32-bit installed. And no third party plug-ins were used in the example project.
Cubase 7.5 64-bit / 7.0.6 64-bit / 6.5.4 64-bit; Win 7 SP1 64-bit; Intel Core i7 2.80GHz; 16GB RAM; Focusrite Saffire PRO 40