Well, enough time has passed. The lower branches thrive and grow, but the upper branches have not moved from this point and have no signs of growth.
Oddly enough, the cambium of these branches and the trunk is green, that is, the upper part is alive. This is strange.
I recently failed at a thread graft on one of my elms in which I cut the scion too early... The leaves dried and fell within a week and the branch stayed green for about 5 weeks before it went brown.
Yours isn't a graft but that being said... if your seeing green... I would still just wait it out as frustrating as it is.
I'll wait until the end of May, maybe some part of the trunk will wake up.
In any case, I have time until the fall or next spring to decide what to do - plant in the field and grow a new part of the trunk (about 2/3 of the length), or make and carve deadwood from this 2/3 of the trunk length.