On the oebb.at website no fares are being displayed for travel between Hallstatt and Melk. Instead the words "non-stop ticket not possible" is displayed in the fare column. Am I entering something wrong on the website? Also is it possible to purchase any type of a discount ticket for travel between these two cities? Thanks for any insight into this matter.
The reason you can't find the fare could be that Hallstatt and Melk are in the same fare district (that's how it works in Germany). If so, you need to find out what that fare district is and what is the website of that district. If you are with others, Austrian Rail does sell the Einfach-Raus-Ticket, which is an all day on/off pass for regional trains. It's €28 for 2-5 people but not usable by a single person. I don't think that's it, but you can find the fare from Hallstatt to St. Pölten (€31,20) and from St. Pölten to Melk (€5,40). Using the fastest trains between Attnang-Puchheim and St. Pölten, the trip from Hallstatt to Melk could be done in 3h27m. By regional train (Einfach Raus) it would take 4h18m.
BTW, I don't think the Hallstatt train station is manned, so a ticket automat might be your only option. It the automat doesn't have St. Pölten as a destination, you might have to just get a ticket to Attnang-Puchheim and get your ticket for the rest of the way there. Alternatively, the station at Obertraun, at the south end of the lake is manned, at least during the day. You can get there by bus from Lahn, at the south end of the tunnels.
Hmm, it does say "non-stop" on the English page. On the German side it say durchgehendes, lit. "throughgoing". I would have translated that as connecting or continuous.