Q. If one could not comply with this mitzva (Kabbolas Pnei Horav – visiting or calling on one’s Rov during a Chag – see question 2391 above), during Yom Tov, can one do so on Isru Chag (the day after Yom Tov)?
A. Poskim disagree when a Rov visits Eretz Yisroel, if a local talmid that only keeps one day of Yom Tov and is now celebrating Isru Chag, should call on his Rov that keeps two days. Betzel Hachochma maintains he should, while Beer Moshe writes he does not have to.
In the opposite case. when the Rov celebrates Yisru Chag, and the talmid is still on Yom Tov, Beer Moshe maintains he is exempt while Betzel Hachochma, Teshuvos Vehanhogos, and R”Ch Kanievsky Shlit’a opine he could. (See Taarich Yisroel p. 820).
Moreover, Moadim Uzemanim (4: 317) opines that there is tashlumin (repayment) for seven days after Yom Tov for this mitzva too. (See Piskei Teshuvos 494: 9).
Horav Shlomo Miller’s Shlit’a opinion is that the tashlumim may apply only on Shavuos. (as the Moadim Uzemanim also mentions). However, other inyonim and issues such as Kavod Hatorah,
honoring and learning it, may also apply on Isru Chag.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a