Q. I very much enjoy reading these questions/answers! Here is my first question: What should be done with a mezuza that gets accidentally knocked or is found already knocked down on Shabbat or Yom Tov? … (See question above)
Would a bracha be said on replacing the mezuza on the doorpost if I am putting it back up on Shabbat? And if it is delayed until after Shabbat, does it get a bracha then? What it I didn’t knock it down, but found it laying on the ground and it might have been there for days…also gets a bracha?
Thanks so much

A. See question above (#1059) that it is prohibited to replace the mezuza on Shabbat or Yom Tov, and when reattached on weekdays a brocho is said.
Poskim disagree if a brocho is recited when replacing a mezuza that was taken down intentionally to be checked..
Some Poskim maintain that even if the mezuza after being examined was found to be kasher, you recite a blessing when reattaching, since there was a distinct possibility that it could have been found unacceptable. Therefore one is “masiach da’as” or does not keep in mind replacing it, (unlike when the mezuza was removed for fixing the frame, painting etc). The above is different to the one who takes off his ta’alis temporarily; in that case we rule that no brocho is recited when he dons it again. (Ad’mas Kodesh 18, Shnois Chaim 74, Ma’ase Eliahu 260, Hamezuza Vehilchoseha p. 106 & 141 et. al.) Other Poskim assert that no brocho is recited when it is replaced on the same day. Pischei Mezuzos (29: 1, p. 305) recommends waiting until the next day, and then reattach it with a brocho. (Aruch Hashulchan Y.D. 289: 4)
Horav Shlomo Miller’s Shlit”a opinion is that we always avoid reciting brochos when in doubt, and no brocho should be recited even on the next day. Only when enough days have elapsed to warrant that the person has indeed forgotten about replacing the mezuza, a brocho should be said.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a