I had a really hard time with mine and just figured out how to open it a few days ago. Off the top of my head I don't remember if I pushed the two tabs up or pulled them down but I got it open. We're going on a trip this weekend so I'm bringing the trailer home tomorrow evening. If you don't get an answer by then I'll take a picture of how I opened mine and post it.
2017 Silverado 3500 Z71 CC / L5P Duramax/Allison
2018 Grand Design Reflection 311 BHS
2015 Coachmen Apex 259BHSS 50th Anniversary (sold)