Keurig troubleshooting can brew a small cup of coffee, not a medium and large cup of coffee. I watched the water resovoir and the water level is not filling the keurig.

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.

Defective circuit board...replace and call factory for reset instructions.

Hello, Irwin -

Those "small gritty black particles" are most likely coffee grounds which are so small they slip into the hot water and eventually the brewed coffee.

The grind size of your coffee may be too fine. Drip coffee method coffee makers, including the Keurig, require medium or medium-fine grind coffee.
Source of information:
Coffee Grind Size: Why It Matters and What You Should be Using, by Taylor Martin, December 22, 2015
CNET Best Products
https://www.cnet.com/how-to/coffee-grind-size-why-it-matters-and-what-you-should-be-using/

You may wish to check your coffee maker to determine if coffee grounds leaked into the space between the k-cup and the k-cup holder:
https://www.youtube.com/watch?v=jZrQhlQpLbs

Best wishes.

Hi,

Here is a tip that I wrote that will give you some things to try that will helpyou get your Keurig coffee brewer workingagain.

Keurig CoffeeBrewer not making a full cup of Coffee
heatman101

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Hi,

Here is a tip that I wrote that will give you some things to try that will helpyou get your Keurig coffee brewer workingagain.

Keurig CoffeeBrewer not making a full cup of Coffee
heatman101

';';

Hi,

Here is a tip that I wrote that will give you some things to try that will helpyou get your Keurig coffee brewer workingagain.

Keurig CoffeeBrewer not making a full cup of Coffee
heatman101

,.
,,
,.

Hi,

Here is a tip that I wrote that will give you some things to try that will help you get your Keurig coffee brewer working again.

Keurig Coffee Brewer not making a full cup of Coffee

heatman101

Hi,

Here is a tip that I wrote that will give you some things to try that will helpyou get your Keurig coffee brewer workingagain.

Keurig CoffeeBrewer not making a full cup of Coffee
heatman101

';
';

Missing seal

I have have the same problem first thing in the morning. My first cup, I press large but with no K-cup; it comes out small or medium. I put the water aside (pour it back into the reservoir after it cools.) Then I brew a large cup using a K-cup, and it comes out the right size. I still want to know how to fix the problem, but at least this works for now.