Dear Guest,
If you are referring to legacy 3D viewer in Browser app, it has been retired (irrespective of the license).
In case , you are referring to the 3D viewer (new) , it is available to all users from the Connect for Browser. We have noted issues in its loading and investigating the same.
Hope this answers your query. Please let us know if you have further questions.
Regards
Darshan Kamat
cc// @Jari Juntunen