Velocity international reward seats have dried up for many months now. If Business Reward is greyed out, it means its not available (either lack of seat offered to Velocity or the limited seats have already been snapped up). Business reward seats costs the least points hence are very limited. Flights to Europe and USA are very popular, hence it is not surprising that you can’t see much availability left. Try to book 11/12 months in advance if possible to increase your chances.
Since you have status with Velocity, it wouldn’t hurt to give them a call and ask them what is going on and ask them to help you find some availabilities.
Alternatively, consider transferring your Velocity pts to Krisflyer and redeem directly with them. Singapore Airlines retain more award seats for Krisflyer members.
If surcharge is an issue, wait to redeem with Krisflyer after 23th of March as a change to their program has been announced yesterday. Have a read of the Point Hack article if you haven’t already.