There are engineering works planned in Denmark that week and night trains definitely won't run. There will be rail replacement buses for part of the journey for daytime trains. You can check timetables on bahn.com.

As a good alternative I'd suggest daytime or overnight ferries between Rostock and Trelleborg : 30% discount with Interrail/Eurail. Go to stenaline.com and add EURAIL2023 as a discount code.

There would also be the night train between Malmö and Stockholm (22:32 - 05:37). Book on sj.se

Probably because of engineering works and timetables that are not final yet. Have you tried asking the operators?

There will be no night trains running between Sweden and Germany between 21/7 and 31/7 due to the track works in Denmark, this according to the information I got in the Swedish FB group for train travellers.

The day trains have a replacement bus for part of the route, but it is not possible to put night train passengers on a replacement bus in the middle of the night. 

It could be the construction work from Copenhagen to Hamburg. If your planned journey has been impacted on these dates, Snälltåget has made the following trains available for Eurail Passholders as compensation between 22nd and 31st July. They all have a stop in Hamburg as well. See the full list of trains, here.