Depending on your 5V power supply, it may be that MaxM is not getting enough current. MaxM needs at least 0.250A at 5V.
And while MaxM is extremely bright compared to traditional LEDs, LEDs are much less bright than normal light bulbs. Compare LED-based replacement bulbs to your 20W bulb and you'll see that to get comparable brightness from LEDs, you'll need to spend a lot of money.
MaxM isn't meant to be a replacement for traditional bulbs. It can do things bulbs can't do though, like be any RGB color and drive flexible LED strip: