1. There is some confusion over models. I've seen "B40" models and instructions with only one size cup button, both labeled B40. I own one stamped "B40" on the bottom, and it has two buttons -- small and large. FWIW, small = 8 oz, large = 10 oz.
2. These reset instructions from another site seemed to do something
What to Do If Your Keurig Won Brew Cup Barista
So.. this is what I did that worked for mine: 1) Hold down Auto-Off and LARGE cup at same time. (all lights should hold steady ON) 2) press SMALL cup while still holding Auto-Off and LARGE cup 3) Release all three, press LARGE cup again.. all lights should go off. 4) Unplug for about 5 - 10 second, plug back in. SHOULD WORK!
3. On *_my_* B40, remove the K-cup, close the door, fill the reservoir. Unplug and replug the B40. All lights should be off.
Pressing "Auto Off" and "Large Cup" together will turn on 3 lights (Heating, Add Water, Power) for about 3 seconds. Doesn't matter how long the buttons are pressed or what order they are released.
I tried lots of add-on combinations: e.g. press button x, press x multiple times, press x while lights are still on, press x after lights are off, press buttons x and y together, press x then y, press x and/or y while still holding Auto and Large, release Auto but not Large and press x, etc.
Nothing gave any confirmation that a reset was accepted. All lights always turned off after 3 seconds. Maybe Reset is only 1 step, i.e. Auto+Large together?