Micro wave cuts out after 20ish seconds

Question edited for clarity and add maker.

Panasonic and Sharp are the brand leaders in microwave ovens. The build quality in the old ones is outstanding. I owned a large one in a commercial pub kitchen reheating hundreds of thousands of meal items for 18 years and it never went wrong once!

This is the manual for the 883 model as a PDF file

https://www.mediafire.com/file/eulp6ogpd6nc3d8

There is nothing for your model, not even on the Panasonic website.

https://www.google.com/search?q=Turbo+bake+NN-A880WBBPQ+manual

..

You can clear it if doesnt take it to the technician its must be reseted

Demonstration Mode
This is to enable you to experiment setting various
programs. (The letter D will always appear in the display
window. This is to confirm that there is no microwave
power produced and it is safe to use the oven without
any food). To set Demonstration Mode: press micro
power once, then press Stop/Cancel 4 times. To cancel
Demonstration Mode press Micro power once, then
press Stop/Cancel 4 times.

To set Demonstration Mode: press micro power once, then press Stop/Cancel 4 times. To cancel Demonstration Mode press Micro power once, then press Stop/Cancel 4 times.

Here are is the manual:
http://service.us.panasonic.com/OPERMANPDF/NNT888S.PDF
Page 13 tells how to shut off Demo mode. (Press FUNCTION-0-2.)

The letter "d" is indicating the microwave is in a demo/learning feature.
To cancel the "demo" mode press and hold "Kitchen Timer" for 5 seconds. Two tones will sound and the small "d" will disappear from the display.

The manual says "while in standby mode, press and hold the '3' key on the keypad for 3 seconds until 2 tones sound and the 'DEMO' icon appears. Repeat to turn demo mode off."

You can download a copy of the manual here:

http://shared.whirlpoolcorp.com/assets/pdfs/literature/Use%20and%20Care%20Guide%20-%208206572.pdf

If it stops after 22 seconds, that means the controller has detected a problem, usually a problem with the inverter or a bad magnetron.

Due to the lethal voltages used and produced, I do not recommend that an inexperienced person work on these.

You can find an authorized Panasonic servicer here.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

Pressing "timer/clock" button 4 times turns on and off demo mode.

In most cases, this is a problem with the inverter or a bad magnetron.

Due to the lethal voltages used and produced, I do not recommend that an inexperienced person work on these.

I would recommend that you contact your nearest Panasonic-authorized servicer. You can find one here:

http://www.panasonic.co.in/