Regular keyboards use 6-key rollover (6KRO), meaning they can only register six keys pressed at once.
Higher-end keyboards like the Dygma Defy or Dygma Raise 2 use N-key rollover (NKRO), which means they can register any combination of keys pressed simultaneously.
Unfortunately, some computers only accept 6KRO on the BIOS or login screen. This can also be an issue with pre-boot encryption, such as Bitlocker or FileVault, and with the PlayStation.
If you have a Dygma Raise, you can update your keyboard to the 0.3.7 - 6kro version of the firmware, and it will work in those scenarios, but keep in mind that your keyboard will be 6KRO all the time.
We're working on a similar firmware for the Dygma Defy and Dygma Raise 2.
In the future, we want to make the keyboard change "modes" between 6KRO and NKRO so that it can be used in these special cases.