How do I book the EuroNight Sweden 345 from Copenhagen Airport to Berlin - unable to find reservetion

You should be able to book it on sj.se, adding the interrail discount

You can’t make reservations from the app. And don’t book at Interrails own booking site if you can avoid it - it adds a €2 booking fee.

Reservations for SJ trains is best booked at sj.se. They have just changed their booking system for journeys after June 4. So things looks a little different from som guides you might find (Like this one: https://www.interrail.eu/en/book-reservations/how-do-i-book-seats.

Here is my instructions for the new SJ booking system. This might also be useful for other users:

• Go to https://www.sj.se/. Or  https://www.sj.se/en for the English version (These instructions will be based on the English version).
• Click “Search journey”.
• Choose travle date. This is to determine if you will be using the old or new system. This step might disappear after June 4.
• Select your departure and arrival stations. You can also change departure date again.
• Now you should tell the system that you have an Interrail/Eurail pass and therefore only need a reservation. This step has changed a little from the old system: Click “Customise” next to “Traveller 1”.
• Click “Travels with travel card”. A dropdown menu appears. Select “Interrail or Eurail”.
• Enter your pass number in “Card number”. It currently looks like there is no validation. For test purposes you can enter anything, but for a real reservation you should enter a valid pass number, since it is printed on the final ticket.
•  Click “Save”
• Add more travelers if needed.
• Choose your journey.
• Choose travel class. 1. og 2. class for day trains. Seat, couchette or sleeping compartment for night trains. Make sure the pass is valid for the class.
• Choose private or shared compartment.
• For shared compartment, choose between men’s, women’s or mixed compartments.
• Choose flexibility. “Non-rebookable” tickets will be full price, so just choose “Refundable”.
• Click “Continue”.
• Unlike the old system, there is no option to choose between upper, middle or lower bed/berth. I hope this will be fixed. If needed, keep trying in new browser tabs until you get the type of bed you want. If you book a shared compartment from Copenhagen at 00:10, I suggest you try to get a lower bed, to disturb the other passengers as little as possible - they might already be sleeping.
• Click “Go to checkout”.
• Enter name(s), Contact details and payment method and click “Pay”

Palle Dam

There is now a validation and you need a valid pass number, preferably a 6 character mobile pass number. 

AFAIK you can't book a private compartment with SJ if you have Interrail. 

Don’t know if is just for me or a general new issue:

When entering the interrail passnumber, it is not correctly validated. One cannot continue the booking.

I also tested with a valid passnumber and a valid mobile pass number.

As of now, no booking on sj.se is possible with interrail.

Works for me, with a mobile pass number (6 characters).

Huh ok. I have another pass, which is also working. Both are bought the same day, but one is already activated for the travel time in november, the other one is not. I guess I’ll write to sj and see what the say.

Thanks for testing!

Last time I booked with SJ, the pass number didn't appear on the reservation. They've changed the backend booking system though, so I don't know if that's still the case. Maybe @AnnaB knows?

Did sj policy changed recently? No Eurail or Interail discount on private compartment. Would have loved to know that before buying Eurail pass. Waste of money.

I can book a private compartment with shower/wc (Hamburg-Stockholm on 12/11):

For the private compartment without shower/wc in the compartment (which they call 2nd class), no Interrail/Eurail fare is indicated, which is very strange if you CAN book the more luxurious compartment with Interrail/Eurail.

I'd ask them via social media, e.g. Facebook, what the problem is and how you can book.

I don't think that you can book a private 2nd class sleeper with Interrail/Eurail. 

Why not when you can book a “1st class” private sleeper?