Rabbi Ovadia Yosef (Teshuva in Yalkut Yosef, Hilchot Nefilat Apaim, § 23) and Rabbi Betzalel Stern (Shu”t Betzel HaHochma, vol. 3, § 14) write that on the day of a HachnasatSeferTorah (inaugurating a newTorah scroll), Tahanunis not recited, and this is the Moroccan custom as well. A newSeferTorahimbues a day with immense joy and therefore the supplication prayers are suspended. Similarly, Rabbi Yehuda Ayash (Bet Yehuda, vol. 1, Yore De’a, § 23) writes that the “Sheheheyanu” blessing should be recited the firsttime a newSeferTorahis taken out and read, and this was also the custom in Morocco.
Rabbi Haim Benvenisti (Sheyare Knesset HaGedola), Rabbi Haim Palagi (Kaf HaHaim) and Rabbi Davi Pardo (Michtam LeDavid) write that in several Sephardic lands, including Morocco, the sponsor of the newTorah scroll would host a feast in his home for seven days and this would culminate with escorting the scroll to the synagogue. Nowadays, such lavishness is less common and the sponsors tend to host a festive meal on the day of the HachnasatSeferTorahitself.
Summary: Tahanunis ommitted on the day of HachnasatSeferTorah. “Sheheheyanu” is recited the firsttime a newSeferTorah is read.