Call to undefined function WPTelegram\FormatText\mb_detect_encoding

From version 4.0.2 i get error when publish new post in Vietnamese

Thông tin lỗi
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Có lỗi E_ERROR tại dòng 208 trong file: /home/cznvqpgq/***/wp-content/plugins/wptelegram/includes/format-text/src/HtmlConverter.php. Thông báo lỗi: Uncaught Error: Call to undefined function WPTelegram\FormatText\mb_detect_encoding() in /home/cznvqpgq/***/wp-content/plugins/wptelegram/includes/format-text/src/HtmlConverter.php:208
Stack trace:
#0 /home/cznvqpgq/***/wp-content/plugins/wptelegram/includes/format-text/src/HtmlConverter.php(122): WPTelegram\FormatText\HtmlConverter->createDOMDocument(‘”Chanh \xC4\x91\xC3\xA0o…’)
#1 /home/cznvqpgq/***/wp-content/plugins/wptelegram/includes/Utils.php(493): WPTelegram\FormatText\HtmlConverter->convert(‘”Chanh \xC4\x91\xC3\xA0o…’)
#2 /home/cznvqpgq/***/wp-content/plugins/wptelegram/includes/Utils.php(551): WPTelegram\Core\includes\Utils::prepare_content(‘”Chanh \xC4\x91\xC3\xA0o…’, Array)
#3 /home/cznvqpgq/***/wp-content/plugins/wptelegram/modules/p2tg/PostSender.php(1142): WPTelegram\Core\includes\Utils::smart_trim_excerpt(‘”Chanh \xC4\x91\xC3\xA0o…’, Array)
#4 /home/cznvqpgq/***/wp-content/plugins/wptelegram/modul