Hi! I have the same problem. I suspect a visit at any German big station is needed to book a seat. It’s obviously not as it should be. I will ask my Polish friends in Berlin in a few days if these trains are often fully booked in summer months. Perhaps I will need to improvise a little.
Reservations from Germany to Poland can currently only be made at the ticket office, or by phone via DB (+49 30 2970, collect at a DB ticket machine).
It should also be possible in other countries than Germany or Poland.
There is indeed just 1 train Direct (means no change, but still mant stops)/day, but you can go much more often-in case you find problems-use the B->WAW direct train and change somewhere-most often Poznan. Note that this trip is very slow the last part, so slow that most local Polski use a bus instead (from Katowice or sometimes even Wroclaw). Do NOT use app-planner, use bahn.de and break up in segments for more options.
You can also go via/change in WAW, this is longer in KM, probably not in time but trains=pociagow Waw->Krk will then be higher chance of full. In PL its most often very busy for tipical weekends-and in summer to/fro the seaside. Trains IN PL are only open for RES 30 days advance-and I just read it should in fact now be possible to do an online seat-ONLY RESERv via the intercity.pkp.pl site-with some tricks. Expect the whole thing to turn into Polish.
Same problem here
@Vidar Smits
If you make a new post where you write your travel details (departure date, time and route) you will get advice on how to make reservations.
@AnnaB Berlin Hbf - Krakow Glowny. Departure Date:24-07-2022, Departure time: 10:39
There is a workaround for this (at least worked in 2021): Buy a domestic reservation from Rzepin to Krakow on intercity.pl (should be less than 1 euro) and then buy the reservation from Berlin to Rzepin when you are at a station. It is very unlikely that the whole train from Berlin to Rzepin will be sold out if you have a reservation from Rzepin onwards… because most people will travel to Krakow, Wroclaw, Katowice.