I've already checked numerous forum threads and viewed youtube videos, but I'm still having issues with my model convergence. Even the message ''Contact pair is inactive'' is unclear to me since I've assigned the bonded contact type.
I've even tried to model a simple concrete 100/100/100 mm cube under 20 Mpa pressure and obtain a crushing and cracking plot but without success. 
Bearing in mind that my goal is to eventually model a masonry wall under cyclic (reverse) loading, I'm not sure whether solid65 is the right choice although majority of papers on masonry wall suggested using solid65 because of its cracking and crushing capabilities.