I cannot customize custom widgets anymore after moving WordPress website

Originally posted here.

The situation is the following one: A colleague of mine built a WordPress theme with some custom widgets which need to be configured through /wp-admin/widgets.php.

In the local copy that me and him have installed everything works fine (it's the latest WP, the production database and the theme from bitbucket). The production is ok, but it's impossibile to change the widgets options since every widget has a There are no options for this widget. label.

So I did a setup from scratch: I created a new WP-ready droplet on Digital Ocean, imported the database I have locally (1:1 production since I changed my /etc/hosts to point the production domain to my localhost) and cloned the theme, but still I got the same issue of production: Widgets were not customizable. Also there are no references to localhost in wp_option rows.

tl;dr: With the same database and the same files, the website works fine locally while in the production machine (AWS) and in the staging droplet (DO) widgets are not customizable.