This plugin slug is classic-widgets-with-block-based-widgets, but the current Text Domain is set as classic-and-block-widgets. Please modify the text domain in all source files. Make sure it is equal to the plugin slug. (see https://developer.www.ads-software.com/plugins/internationalization/how-to-internationalize-your-plugin/#text-domains)

Modifications are the following:
classic-and-block-widgets.php
Line 9
Text Domain: classic-widgets-with-block-based-widgets

Line 40
add_submenu_page( 'themes.php', __( 'Classic Widgets', 'classic-widgets-with-block-based-widgets' ), __( 'Classic Widgets', 'classic-widgets-with-block-based-widgets' ), 'edit_theme_options', 'widgets.php?cw=1', null, 3 );

Line 69
. __( 'More Plugins', 'classic-widgets-with-block-based-widgets' )

Line 81
. __( 'Classic Widgets', 'classic-widgets-with-block-based-widgets' )