Hi again,
Ok, lets take this one by one. First off, I don't own any VR titles yet, so I don't know about that. But for regular videos I'm pretty sure you should be able to download them. So as for your first attempt, let me ask you some questions!
1. I noted that you initially used 'mide00070' as your download sample, since this was the free video we received when signing up. This is good, since everyone should have this video (most people anyways!). There is no catalog entry for this video, but downloading it works (I just verified this).
2. In all cases, are you still receiving the "login_required" error? If so then clearly we need to fix your login situation. (^_^); I assume you downloaded the "get cookies.txt" plugin for chrome, added it to your browser, verified that it is running, proceeded to login to your R18 account, verified you logged in by looking at the R18 dropdown menu (to see if the "logout" option is avaliable for you), and then clicked on the "get cookies.txt" plugin icon to export your cookies file to disk? (I'm being verbose because I need more accurate information to verify your workflow). Remember, the plugin only exports your current tabs cookies, so make sure when you click on the icon your viewing the tab where your R18 webpage (logged in) is loaded.
3. The location of your cooikes file does not really matter. Placing it in the Jav-It folder just makes running things easier. However, if you launch Jav-It from another location be aware that your file paths need to be relative to where you are launching it from. To eliminate this posibility, lets just specify fully qualified paths for now. That is, write "c:\temp\r18_cookies.txt" (or whever you saved it) instead of just "r18_cookies.txt".
4. Can you copy the direct output of your run, including the initial command line your using? This will help me figure out what your missing, since your problem seems to be a unique case!