I faced the same behavior on same release and before opening a Feature request I checked here if somelse faced the same.
I added some “admin” rights for the Admin user. I added an ACL with ADMIN right for “CLUSTERS”.
I am not a big fan of this workaround as it means that an external user with admin rights must be cluster administrator to create a Virtual Network. While for me this should not be the case (I will open a feature request for this). @machiasiaweb, can you check if adding some admin rights to this user unlock you situation ?