Am. Standard Oil Burner just changed oil filter,nozzle.new tank and lines. Just had the unit serviced was running for a couple of days then shut off I bypassed the thermostat and it ran for the day however I couldn't get it started since. Could it be a flame out or defective Oil primary Control? Thanks in Advance!

I am sure you had all that work done by a professional?

If not there is the problem.

By changing all these items at the same time(oil filter,nozzle.new tank and lines) many possibilities exist for a failure.

Did you test the ignition transformer for proper voltage output? 7,000 to 10,000 volts with a high voltage tester?
Did you try and pull a arc off the two terminals to see how far the spread before lost contact?
Did you test the oil primary for proper operation?
Did you test the Cad cell for proper operation?
Is the electrode gap and distance from the tip of the nozzle set or was it a best guess?
Did you test the oil pump pressure?
Did you check the king coupling from motor to pump?
Did you set the air over the burner correctly?
Did you adjust the primary air damper?
Did you check the new lines to be sure they are tight and that there were no suction leaks to allow air into the line?
Did you replace the lines exactly like they were removed and to the same location inside the tank. One is longer than the other since one of them has to be near the bottom of the tank to remove oil?
Did you give a slight pitch to the oil tank to give it a debris well area?
Did you replace ALL the gaskets on the oil filter assembly when you changed the filter?

There are many more items that can cause a problem with a oil burner. These are just a sample so you can check for your problem.