Jews everywhere should know that the time for the coming of Moshiach has certainly arrived. All that is needed is to fulfill the directive of the Previous Rebbe: "Stand ready, every one of you, to greet our righteous Moshiach!" These preparations, motivated by a yearning and desire for Moshiach, will of themselves surely bring Moshiach.
As to the question, "Why has he not come until now?"--Moshiach will no doubt provide an answer for this in person. In the meantime, the query must not (G-d forbid) weaken a person's spiritual endeavors. On the contrary, it should spur him ahead with ever more energy.