Deities have largely withdrawn their avatars from Faerun followingas a result of new rules imposed by Ao during the Second Sundering.
The question of exactly why the deities have unilaterally limited their use of avatars following the Second Sundering is as yet unannounced. Forgotten Realms creator Ed Greenwood confirmed that this is the situationappears to have been answered by Wizards of the Coast in their 2012 Gencon panel, but did not explain whyWhat is the Sundering (Part 1): The Overgod Ao established a new paradigm for the gods when dividing Abeir and Toril into separate worlds again:
The godsOnce it is over, the word of Ao declares that the Era of Upheaval is ended. Great stories remain to be told in general seem more "distant" post-Sunderingthis new era, more "heard from" than "personally seenbut they are not the stories of gods and godlike beings. They are the tales of mortal heroes, taking a stand to preserve the world they love.
AsThe first fifteen minutes or so of July 2018, whether a future official Forgotten Realms adventurethis video explain the lore behind this and what Ao's motivations are. The average person in the world has no knowledge of Ao's interactions with the gods, sourcebook oras stated in the "What is the Sundering" panel:
Elminster is probably the only one of these characters [of The Sundering series of novels] who might have any insight into that at all, and I don't think even he has very much.
This makes it unlikely that any given novel answerswill actually explain Ao's interaction, as it's something their protagonists are generally not aware of. Even sourcebooks do not have much information on this question remains to be seen. The Sword Coast Adventurer's Guide states that gods can still manifest on Toril, but only very rarely, and simply explains it as follows:
Though many tales are told of times past when the gods appeared in physical form and walked the land, occasions of that sort are few and far between.