Early versions of PiStorms had two LEDs. For some time during the development of the product is went down to only one on Bank A. Current firmware versions do not support the LED correctly and you may experience such things as only Bank B showing or possibly no LEDs lighting at all. We have since fixed this issues (as well as some motor issues) and are releasing the new firmware version in the next couple of days. I will post the link with instructions once the new firmware is available.
There also is a new firmware available (after you install software, if an upgrade is needed, PiStorms should display exclamation icon on top, You can then upgrade the firmware by clicking on that icon).