i found the problem and post the solution here for others.
the problem was caused by missing access rights. by default the container has no rights to use the folder. but there is no warning or error message, and the server will start, but you cant claim it without the token.
so you have to add a user and group id to the yaml from a user that has read/write access to the folder “teamspeak-data” in my example.
You need to add “user: xx:yy” to the teamspeak section. xx stands for the user ID and yy for the group ID.
I created a new user and group in DSM for the server with Read/Write rights only for this folder. but as far as i know, its not possible to see these ID’s anywhere in DSM. here is a guide that explains how to check them → https://mariushosting.com/synology-how-to-find-uid-userid-and-gid-groupid/
when you found out the ID’s you can enter them in the yaml file, and create the project. after that, the Admin Key is shown in the container protocol and the “teamspeak-data” folder finaly shows the files.