When a flight is not found or the flight shown is not correct it's usually due to one of the following reasons:
A wrong date: Make sure you get the date from the itinerary and not your calendar, as the time zone difference might give you the wrong date.
The wrong year: Make sure you select the correct year of your flight.
The flight has been cancelled: Check with your travel agency.
The flight number is incorrect: Be careful with the two letters and check that they are correct. We've noticed that travel agencies sometimes make mistakes.
If none of the above apply, please reach out and I will see what I can do π