When scaling, the menu disappears, why?

Question

Bootstrap

Why when I change the scale of the site (for example, 150%), a button appears (this is understandable, for mobile browsers and all that). Interested in something else, why when scaling back, the menu does not appear?

Answer 1

On the bootstrap site, everything is OK, in fact, no problems should arise. So we are waiting for links or code.
upd:
try adding navbar-collapse class

<div class="navbar-collapse container-fluid nav-collapse collapse">
...
</div>

Answer 2

summer, telepaths on vacation.