Are reservation required to travel by train from Copenhagen to Amsterdam? Have tried to make auroral reservations but reserved seats aren't available for the connections through Hamburg
When? And where are you trying to make reservations? It can be required between Copenhagen and Hamburg but usuallly not between Hamburg and Amsterdam,
We're traveling on July 28th, it seems as if the there are seats available between Hamburg and Amsterdam bu they aren't available for reservation. I think we could get reserved seats from Copenhagen to Hamburg
You can always buy a seat reservation directly from Deutsche Bahn. Be aware that some of the connections are with regional trains that do not have seat reservations. Cost is 4.50 EUR for a given itinerary. In fact, you could buy the seat reservation all the way from Copenhagen to Amsterdam from Deutsche Bahn for 4.50 EUR and forget Eurail.
Reservations are not required, but recommended for the Copenhagen to Hamburg leg as it can be crowded.