Trial Expired before 90 Days

I’ve been doing everything I could to unexpire it. I tried redownloading the exe and nothing works. The day after downloading it suddenly expired. I don’t know what to do! I’m a student and I wanted to use this for a project,but I need a trial before considering buying.

http://discourse.mcneel.com/t/rhino-evaluation-expired-before-90-days/9369/8