My problem was solved after contacting vray support.
Here's what did it:
Make sure VRLService is running. You can check that by going to Task Manger > Services.
It wasn't running...so, on to step 2
Download and install V-Ray license server:
https://download.chaosgroup.com/downloads/289/download
Installed it, then ran 'Manage Vray Online License Server'
Good to go....now I'm having fun with the 3.0 beta. UI is gonna take some getting used to...but some real cool features so far 
I'm having the same problems. This is how my config.json reads:
{
"local": {
"vrolHost": "0.0.0.0",
"vrolPort": 30304,
"dongleEnabled": true,
"vrlPort": 30314
},
"portal": "https://ols.chaosgroup.com",
"diagnostics": {
"level": "debug"
},
"proxy": {
"host": "",
"port": 0,
"type": "none",
"username": "",
"password": ""
}
}
Can anyone edit this for me? (I'm not sure how to add the localhost:30304/ 127.0.0.1:30304 IP as exception....I'm a 3D artist, not a programmer! )
Have thought about writing a 'light lister' script for Vray SKU? (I'm currently manually resetting subdivs on 20+ lights in a scene...fun, fun!)
Wow! Itil, this is an incredible collection of tools. Thanks so much! I can't believe how much time this could save. Will be very handy while waiting for Vray3. Cheers! 
In a situation like this, I would heavily desaturate/lighten the sand, render the scene out, then add the sand during post. Make sure you have render ID or Material ID selected in your render elements (for masking/selections). You'll easily be able to apply color and texture to your sand while keeping you shadow data by using layers/masks/blend modes in photoshop. With a little googling, you can find some great tutorials that explain how to do this in detail. I wouldn't change anything on your original arch model. I think it's more important for your building materials to be reflecting proper lighting/colors on themselves. cheers.