What is your question?

Which train is this? (route, departure time)

I would like to know if I can Take this train 

Yes, this happens sometimes-and in some areas now fairly often. Also due to fewer trains run due to shortage of staff.

This is one of the wonders on the INterRail -pass; later you can tell your grandchildren: what granpa has experienced when he was still young………..even worse as that state run SNCF was able to do!

THis is also a hidden incentive to use brains and not just those planners from the web-make plan B.

Yes but it doesnt answer to me

Until 21/8 you need a reservation on this train.

During the summer there is mandatory reservation on the direct trains between Germany and Denmark. 

Here you can make reservations for the train, if there still are seats available. 

https://travel.b-europe.com/dsb-rail/en/reservation-only#TravelWish

Would I be right that the first “reservation” you refer to was entering it into your trip and then into your pass when you activated it, and the pass didn't warn you a separate seat reservation was required. Unfortunately, as you will read all over the community posts, that is not a reservation but just creating a travel ticket. Reservations for trains requiring them need to acquired from other sources.

Note: no train entered into your pass includes a seat reservation - the planner will guide you with reasonable accuracy to those requiring an additional reservation, (but it is always worth looking on the community for tips to avoid these trains)

A quick check on the Interrail planner does indeed show that journey tomorrow does require a reservation, so today’s would have been the same.

Had you known, If you had been at Hamburg early enough you could go to the ticket office and either got a reservation or created a plan B.

Only with a reservation. You also need to update your app. You're still using an older version, the one in which the notice about the mandatory reservation was missing.