Fatal Error in Activation

When I updated to 0.15.2, the results page went blank when I filled out the test. Tried to deactivate and activate the plugin, and I get this error:

Fatal error: Class ‘mysqli’ not found in /home/ndddev/public_html/awakenings/wp-content/plugins/wp-testing/vendor/ruckusing/ruckusing-migrations/lib/Ruckusing/Adapter/MySQL/Base.php on line 1137

Tried to delete and reinstall and I get the same error. This is what line 1137 has in Base.php:

$this->conn = new mysqli($db_info[‘host’], $db_info[‘user’], $db_info[‘password’], ”, $db_info[‘port’], $db_info[‘socket’]); //db name leaved for selection

How can I fix this?

https://ww.wp.xz.cn/plugins/wp-testing/