Uncaught Error: Call to undefined function simplehtmldom_1_5

I tried to export but failed.

Activity Log

[2016-10-01 15:58:10] Amo has started generating static files
[2016-10-01 15:58:10] Setting up
[2016-10-01 15:58:11] Error: (1) Uncaught Error: Call to undefined function simplehtmldom_1_5\mb_detect_encoding() in /var/www/html/recordsfromshelf/wp-content/plugins/simply-static/includes/libraries/PhpSimple/simplehtmldom_1_5/simple_html_dom.php:1248 Stack trace: #0 /var/www/html/recordsfromshelf/wp-content/plugins/simply-static/includes/libraries/PhpSimple/simplehtmldom_1_5/simple_html_dom.php(1084): simplehtmldom_1_5\simple_html_dom->parse_charset() #1 /var/www/html/recordsfromshelf/wp-content/plugins/simply-static/includes/libraries/PhpSimple/simplehtmldom_1_5/simple_html_dom.php(102): simplehtmldom_1_5\simple_html_dom->load(‘…’, true, false) #2 [internal function]: simplehtmldom_1_5\str_get_html(‘…’, true, true, ‘UTF-8’, false, ‘\r\n’, ‘ ‘) #3 /var/www/html/recordsfromshelf/wp-content/plugins/simply-static/includes/libraries/PhpSimple/HtmlDomParser.php(21): call_user_func_array(‘\\simplehtmldom_…’, Array) #4 /var/www/html/recordsfromshelf/wp-content/plugins/simply-static/includes/class-simply-static in /var/www/html/recordsfromshelf/wp-content/plugins/simply-static/includes/libraries/PhpSimple/simplehtmldom_1_5/simple_html_dom.php on line 1248

Export Log

200 http://www.recordsfromshelf.com/ —
http://www.recordsfromshelf.com/wp-includes/js/wp-emoji-release.min.js —

Any help is appreciated.