I can find a timetable for a direct train on google maps but not on trainline or omio. I was looking for Berlin-Quedlinburg around June 15th
The license for that line run by Transdev expired by the end of 2018. It's now operated by Abellio. Tickets are available aboard the train.
A press statement from Dec 2018 says that the route was taken over by Abellio Rail Mitteldeutschland. Do not know the details but it seems the route itself was changed.
Also check Deutsche Bahn for a connection.
Don't ever use google maps for this kind of thing, use Deutsche Bahn website. Last time I looked, Google does not operate any trains.