External orgs tab missing / External shared workspace is not available in service

We received an invitation from external company as guest . They have added us to their workspace as collaborator. We could not able to locate that workpace in our PowerBI account or publish our report to that workspace from PowerBI Desktop app.Our requirement is to share our workspace to that workspace with limited access (viewer) or an option to publish our report to their workspace with limited access. What are the ways to do this.