Run few seconds then quits flashing 3 green lights

You have a fault that no one else has, so I am guessing it is a feature. Google

make model manual

https://www.google.com/search?safe=off&rlz=1C1QJDB_enCA643CA644&sxsrf=ALeKk00XjIH4Nu5Q0bcIS_B3NNSNT0I7yQ%3A1615855533664&ei=rf9PYJrsJ9ej5NoPveelsA0&q=Frigidaire+Gallery+Dishwasher%2C++blue+light+flashes+twice+at+5+sec+interval

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Sounds like either the wash pump brushes have worn, or more likely the pcb timer is faulty

It sounds like you just need to reset the controller. This is done by running (or partially running) a diagnostic cycle, which will clear the error. Here's how to do it: Depending on the model, and the keys you have, press the following sequence of keys quickly (with less that 1 second between key presses:
Heated Dry - Normal - Heated Dry - Normal; or
High Temp - Air Dry - High Temp - Air Dry; or
Hi Temp Scrub, Energy Saver Dry, Hi Temp Scrub, Energy Saver Dry; or
High Temp Wash, Heated Dry, High Temp Wash, Heated Dry.
You will know that you have entered the diagnostic cycle when all the lights light up. Let it run for a few minutes, and then press Cancel to stop the diagnostic cycle and clear the error.

Note: On some of the newer Whirlpool, Kenmore, KitchenAid dishwashers, you start the diagnostic cycle by rapidly pressing the 3 left-most keys in the following sequence: 1 2 3, 1 2 3, 1 2 3.

If you need further help, reach me via phone at https://www.6ya.com/expert/ronald_e6b9572cebe3ad27

An amber light means your computer isn't reading the hard drive or CD right, Take it to a professional to get this corrected

Communication error between indoor to out door.Comms Error, check your wiring, remove external pumps. Split/Multi - check volts from terminal N to 3 = 0 - 65 Vdc, Multi V - 4 Vdc terminals 3 and 4

It is in a delay wash mode.
Disconnect power for 60 seconds.
Re-connect power.
Press the Cancel button.
Press the regular wash cycle and start the dw.

hold the start button for 3-4 seconds and see what that does

I solved my problem by disconnecting from the power source and then reconnecting, apparently it needed to be reset, it now works fine!

I actually had to change the steps a little and this is what I did:

press heated dry
press normal wash
press heated dry again
press normal wash again
wait a few seconds
all the lights should come on
press cancel (should hear pump)
hit cancel again

Started a cycle and began washing.....Thx

If you have had a lightning storm or power surge it may have fried the electronics panel. That is what happened to mine. Once it is fixed you should put a surge suppressor on it that is rated for major appliances.