Gantt chart does not appear

There are two tabs. (A-tab, B-tab) And A-tab has a Gantt chart.
When the page loads, the Gantt chart looks fine. However, I go to B-tab and load the Gantt chart and I go to A-tab, the Gantt chart does not appear.

You need to check the Dev Tools on the Console tab. Probably there is an error message.
I suppose you use React, Angular, Vue, Svelte, or something else. In that case, it is good to use the Gantt instance approach.
When you open a page/tab/view with Gantt, you need to create a new Gantt instance. When you switch to a different page/tab/view, you need to destroy the Gantt instance:

Alternatively, you need to manually reset everything by yourself.
The following article covers the known issues:

If that doesn’t help you, it is hard to suggest what might be wrong as I don’t see your code. In that case, please, send me a ready demo with all the necessary Javascript and CSS files so that I can reproduce the issue locally.