Undefined variable $wp_filesystem

Hi – trying to take this good-looking plugin for a test drive, but hitting the following error after configuring favicon and clicking on the final save button: AH01071: Got error ‘PHP message: PHP Warning: Undefined variable $wp_filesystem in /class-favicon-by-realfavicongenerator-api-response.php on line 208 PHP message: PHP Fatal error: Uncaught TypeError: get_class(): Argument #1 ($object) must be of type object, null given in /class-favicon-by-realfavicongenerator-api-response.php:208 Stack trace: /class-favicon-by-realfavicongenerator-api-response.php(166): Favicon_By_RealFaviconGenerator_Api_Response->downloadZipFile() /class-favicon-by-realfavicongenerator-admin.php(215): Favicon_By_RealFaviconGenerator_Api_Response->downloadAndUnpack() /class-wp-hook.php(324): Favicon_By_RealFaviconGenerator_Admin->install_new_favicon() /class-wp-hook.php(348): WP_Hook->apply_…’, referer: /themes.php?page=favicon-by-realfavicongenerator%2Fadmin%2Fclass-favicon-by-realfavicongenerator-admin.phpfavicon_appearance_menu&json_result_url=%2Fapi%2Finteractive-requests%2Feaf70d99-2165-44a1-97c8-db7828fcc580 WordPress Version is 6.6.2, PHP 8.