If you look like some of us in Pro Game Guides, then perhaps you have reached a point in Hogwarts’s Heritage, when you cannot start your next main quest.
There may be a variety of reasons for this, but the most likely of them is what you may not expect, despite the fact that the game tells you about this at an early stage.
If you are, continue to read, because after long trials and errors, we, fortunately, found out how to move on to the next quest in the line of quests Preparation for owls.

How to unlock the next main plot quest after in the shadow of the mountain is the Hogwarts Heritage

We are sure that we are not the only ones who monitor the excitement that causes the shadow of the mountain quest, but what happens after it may be a problem if you have not read your letters from OWL Post, which come daily.
This is quite reasonable, because your main quest usually just continues, regardless of whether you have read any of the letters.
However, for the quest Preparation for owls you need to do just that in order to launch the next main quest.
We wandered around the magical world for hours, performing side quests and exploring the countryside in the hope that the next main quest will begin after some accidental completion.
Alas, this did not happen.
Instead, you will need to open your OWL Post letters and find a letter from your Goblin friend, Look.
It turns out that Look was looking for a mine and earlier mentioned that he would send an owl letter as soon as he found it.

This is the same letter.
After the opening of the letter, your main quest should continue where they left, sending you to the aid of Look in the destruction of the Drink Wing.
Personally, I can say that I was pretty upset when this happened, because I thought that they could listen to me.
Fortunately, since I have already passed the game, I can confirm that after that there are no other quests that make you read the letters of the Owl.
To obtain additional quality manuals, tips, hints and information regarding Hogwarts’s heritage, get acquainted with our leadership Hogwarts’s legacy-the difference between Levies and Wingardium Levies, the explanation right here in Pro Game Guides.