A similar question was raised on another thread.
I've checked with Development to confirm, and, unlike Network Atlas, which you can use from remote locations that can access your SolarWinds database, Report Writer must run on your primary SolarWinds (Orion Core) server. Reports are always viewable remotely, using multiple methods, including exported pdf, web console URL, .xls, and additional web server, but, if you want the ability to edit reports, you need to log in to the primary server, typically via RDP, and use Report Writer there.
Please feel free to submit a feature request. This thread has also been marked for PM review.