A technical overhaul and Unity upgrades - "A series of unfortunate events"
Battletech's backer beta was scheduled to start on 15 March 2017 but has now been delayed until some back end technical issues can be resolved and the dev team upgrades to a newer version of Unity.
HBS
"HBS has a history of toughing it out and working with sub-optimal back-end tools because we want as much development time as possible to be spent on game features and fun. Eventually however, a system becomes too painful to use and we bite the bullet and pay the development price" - senior producer on the project with Harebrained Schemes, Chris Klimecky announced on the game's page and added that, "Now, we know from experience that whenever you update major software in the middle of development things WILL break, so we diligently planned time for integration and bug fixing. Unfortunately, while the upgrade succeeded in improving the game’s performance, the changes in Unity broke a lot more of our systems than anticipated."
The team wont be announcing a definite release date until they are certain that no more delays will happen. Presently Battletech is roughly looking at a Late Summer/Fall release.