I have done it WRONG myself. The Vienna Assistant did not log me into my account. Obviously this was turned off in the settings (for whatever reason).
After logging in, BBO was also made available for installation.

Unfortunately, this did not solve the problem for me.
But again from the beginning:
Originally the license of the BBO Free ran with the eLicenser.
With the Celestial Strings I wanted to change completely to iLok. After several div. tries Celestial Stings is now displayed and playable in the SyncronPlayer, BBO Free is not. All licenses are transferred to the machine with the iLok Licenze Manager.
I have downloaded and installed BBO Free with the download manager. Also the NKS implementation. In NI-Complete the BBO is displayed, but files are not loaded (error message).
In the Vienna Assistant I have deleted eLicenser libraries and with BBO Free everything again from the beginning, unfortunately without success.
Now I do not know unfortunately no more further - THX for your help

Win 10