Ionic 5 - ion-content doesn't have a visible overflow (cannot scroll)

I am working on migrating an Ionic 3 / Angular 5 app to Ionic 5 / Angular 11 and I have a problem with the layout of the page: when I use ion-header and ion-content , the content of the page is not scrollable. Here is my code:

<ion-header>
    <ion-toolbar>
        <ion-item lines="none">
            <ion-label>
                <ion-title>My title</ion-title>
            </ion-label>
        </ion-item>
</ion-toolbar>

<ion-content>
    <!-- A lot of content here -->
    <!-- This is not scrollable -->
</ion-content>

By comparing the new layout with what I have in Ionic 3, while in Ionic 3 the header and the content have an absolute position with a top padding/offset (all these injected by Ionic), in Ionic 5 the position of the content is relative without any top padding. I am not sure if this is the real problem or what am I doing wrong, maybe there is something else I need to set. Is there a setting I can use for Ionic 5 so the problem disappears? Please advise. Thanks!

Ion-content should be srollable by default. So it may be something outside of what you have shown and what you might be doing. That can be anything, from CSS styling or a DOM element covering the ion-content but being transparant and grabbing the scroll event. etc…