Drag and drop not working in composing emails

Hi there, today I don’t manage to compose any emails in my campaigns, the drag and drop function to insert blocks in the emails (text, image, button and the like) is not working.

It’s definitely not because of the mouse 1) because it’s the same mouse I’ve been using so far, 2) because I can use drag and drop to insert snippets into a form.

Any idea what could be wrong and how to fix it?

Thanks,
Letizia