Because updating the Rainmaker is a rather lengthy multistage process, there are a few things that can go wrong and cause it to fail. Luckily you're a smart cookie (otherwise you wouldn't have bought a Rainmaker) and we've got your back.
If you haven't watched it already, this video walkthrough is a good place to start: https://www.youtube.com/watch?v=vxZ_gbtBkcM
The most common issue with firmware updates on the Rainmaker is when the USB Blaster is not detected while trying to update the FPGA portion. Often this is caused by a 32-bit/64-bit mismatch between the versions of Windows and the Quartus Programmer software. So it's worth double checking that you have downloaded the same versions of both items, and that the correct drivers are installed. If you are using a 64-Bit version of Windows, you will need to download the 64-Bit version of Quartus, and install the 64-Bit drivers.
If you are using Virtual Box on a Mac, it is also necessary to allow the device to be seen by Windows. In the bottom left corner of the Virtual Windows box there is an icon for USB devices. If you right click here you can select "USB Settings" and add USB devices that will be usable in Virtual Windows.
Click on the Add USB Device symbol on the right with the green plus sign to add the USB Blaster.
If the USB Blaster is still not detected, it's worth trying a few simple steps to isolate the problem. Try another USB cable, try another USB port, try using a USB hub. Often these can solve the issue.
Some USB cables, especially the ones that come with devices as a means to charge them, are only able to provide power. These ones will not communicate any data with your computer so they will not work for the update.