Train ticket cancelled

This happened to me in 2015, when I booked a three-country Eurail Pass for Poland, Hungary and Austria. I bought the Eurail Pass in the U.S. before my trip.

After four days in Krakow, I was supposed to take the train to Budapest via Katowice, Poland. Before the trip, I was warned that there was construction on the rail between Krakow and Katowice, where I was supposed to switch trains to go through Czechia and Slovakia on the way to Budapest. Eurail in the U.S. said to take the bus between Krakow and Katowice and that the bus service would honor the Eurail Pass. Turns out, the bus didn't honor the Eurail pass: I had to pay extra bus fare. Plus, the bus was late to Katowice, and I had to spend an unscheduled stop there. I got in a day late to Budapest.

If you have a Eurail ticket, make sure everything is in writing and set in advance. I believe Eurail in the U.S. was dishonest and misled me about the bus ticket between Krakow and Katowice.

Otherwise, you might have to do the same as I did: spend an unscheduled stop somewhere. In the end, I enjoyed seeing Katowice, a fascinating industrial town being reborn as an edgy tourist destination few Americans -- and probably Europeans -- get to see.

The issue here is that Keleti station is closed for construction work, with trains diverted to Budapest Kelenfold.

In general the trains are departing Vienna at their normal time, just serving a different Budapest station. As OeBB have said your ticket remains valid, so nothing to do, by you, except go to Kelenfold station in Budapest.

Others will tell you how to accomplish that.

The Metro will take you directly to the Kelenfold station, just board your train there.

Thats the M4 metro which will probably require 1 change to get on. But you are over 65 or have a travelcard so its free. Relatively small, simple station.