Water tank has a crack in it.

Here is a link to some troubleshooting:
What to Do If Your Keurig Won Brew Cup Barista

I realize you think it does not need descaling to to it 'not being used much.'
However you may have hard water and I would think descaling is definitely worth a try. There might be scale built up on the water level probes in you machine.

Descaling Details are listed below:

Brewer Model: Elite B40 ' Classic B44
Special Edition B60 ' Platinum B70

To begin, you will need the following:
• 48 ounces of undiluted white vinegar
• Large ceramic mug (do not use a paper cup)
• Access to an empty sink

PREPARE
Step 1:
Empty the water in the Water Reservoir.

Step 2:
Disable "Auto Off features."

FILL AND CLEAN
Step 1:
Pour approximately 48 ounces of the vinegar into the Water Reservoir.

Step 2:
Place a large mug on the Drip Tray Plate and run a brew cycle.

(DO NOT USE A K-CUP)

Just press the BREW Button. Pour the contents of the large mug into the sink.

Step 3:
Repeat the brew process without a K-Cup until "ADD WATER"
is indicated.

Step 4:
Now let the Brewer stand for at least 4 hours while still on.

Step 5:
Discard any residual vinegar and rinse the Water Reservoir thoroughly.

RINSE
Step 1:
Ensure the Water Reservoir is filled with fresh water.

Step 2:
Place a large mug on the Drip Tray Plate and water brew cycle. Pour the contents of the large mug into the sink.

Step 3:
Repeat brew process until "ADD WATER is indicated.

Step 4:
You may need to perform additional water brew cycles if you notice any residual taste.

Fill the tank with vinagar and run the machine to empty the tank restart the process for couple of cups live the machine over night run clean water threw the machine you done.

Your b60 may need to be descaled. There might be scale built up on the water level probes in you machine. I have listed the directions below:


Brewer De-Scaling Instructions
Brewer Model: Elite B40 ' Classic B44
Special Edition B60 ' Platinum B70
To begin, you will need the following:
• 48 ounces of undiluted white vinegar
• Large ceramic mug (do not use a paper cup)
• Access to an empty sink
PREPARE
Step 1:
Empty the water in the Water Reservoir.
Step 2:
Disable "Auto Off features."
FILL AND CLEAN
Step 1:
Pour approximately 48 ounces of the vinegar
into the Water Reservoir.
Step 2:
Place a large mug on the Drip Tray Plate and run a brew cycle.

DO NOT USE A K-CUP
, just press the BREW Button. Pour the contents of

the large mug into the sink.
Step 3:
Repeat the brew process without a K-Cup until"ADD WATER"

is indicated.
Step 4:
Now let the Brewer stand for at least 4 hours while still on.

Step 5:
Discard any residual vinegar and rinse the
Water Reservoir thoroughly.
RINSE
Step 1:
Ensure the Water Reservoir is filled with fresh water.

Step 2:
Place a large mug on the Drip Tray Plate and
water brew cycle. Pour the contents of the
large mug into the sink.
Step 3:
Repeat brew process until "ADD WATER is indicated.

Step 4:
You may need to perform additional water brew
cycles if you notice any residual taste.
NOTE:
If "DE-SCALE" is still displayed after
completing the procedure, repeat the
descaling procedure above.

PLugged exit port tube. Manual Page 18

It's time to descale your brewer. Run a full reservoir of pure white vinegar through, and then a full reservoir of water, "brewing" and dumping one cup at a time. You might have to do two reservoirs of vinegar if you've never rescaled it before.

Handle not engaged all of the way. Rest and press firmly in place,

I had this problem too.
I just pressed the small brew button; it pulled some water from the reservoir and heated it but nothing came out. Then I opened and closed the top cop thing and both the cup sizes were flashing and it worked like normal again.

Hi,

There is air in the lines and it is blocking the water flow...
Here is a tip that will help you getyour Keurig to prime...

Keurig CoffeeBrewer will not prime
heatman101

Per Pages 9 and 10 of Keurig Model B40 Use and Care Guide,
1) turn off the "Auto Off "feature
2) fill empty water reservoir with 48 ozs of undiluted white vinegar.
3. Place ceramic cup on the drip tray and run a brew cycle. Do not use a K-cup!
4. Press the large mug Button
- let Keurig coffee maker fill mug with vinegar & empty in sink.
5. Repeat brew process until water reservoir of vinegar is empty. (remember to open and close lid between each cycle so large mug Button will flash.
6. Rinse the water reservoir thoroughly and fill with fresh water.
7. FINAL STEP RINSE CYCLE
a) place a ceramic cup on the drip tray
b) run regular brew cycles WITHOUT using a K-cup.
c) pour rinse water into sink each time.
d) repeat brew process until water reservoir is empty.
d) perform additional rinse cycles if you notice any residual vinegar taste.
e) if the red "De-scale" light remains illuminated after completing descale and rinse cycles, repeat the descaling procedure above.
Otherwise - you're good to go!