Need to catch train Friday 9 September ..Paris to Luxembourg City to meet a biking tour. What train station is best ? Hoping to arrive in Luxembourg city by 15:00 ..18:00 at latest. Is their a fast train .
Paris Est is the station you want. Fast trains with local connecters will get you there in about 3 1/4 hours.
Trains to Luxembourg use Gare de l'Est. https://upload.wikimedia.org/wikipedia/commons/1/1a/Railway_stations_on_departure_from_Paris_map-en.svg
If you don't want the trip with a connection, there are direct TGV's that take a bit over 2 hours, use https://www.sncf-connect.com for more information.
The only direct train gets there at 21:52 on Sept 9, which is later than you want. So unless you can travel on the evening of the 8th, you'll have to put up with a connection.
September is still far away, don't assume that the trains you see now are the only ones that will run in September.
There are 6 direct trains a day from Paris Est to Luxembourg, and it is indeed a bit too soon to have all the trains show up for September. Look again later this month.