If your comment like/dislike system allows people to like more than one time, it means the update process was not finished correctly and some changes in the database was not implemented. We recommend deactivate wpDiscuz and activate it back, then delete all caches and check again. If the problem exists please follow to the instruction below:

This is a database table structure issue. The wp_wc_users_voted table structure is not updated on your website. You should execute this SQL query in phpMyAdmin database manager SQL Tab. You can install phpMyAdmin plugin, or use your Hosting Service cPanel > phpMyAdmin Database Manager > Your website Database > SQL Tab:

ALTER TABLE `wp_wc_users_voted` ADD COLUMN `post_id` BIGINT(20) UNSIGNED NOT NULL DEFAULT 0, ADD COLUMN `date` INT(11) UNSIGNED NOT NULL DEFAULT 0, ADD INDEX `post_id` (`post_id`);

Please check the red marked wp_ prefix. If your database table prefix is different, you should change it to yours.

After, executing the SQL, click on the database name and find wp_wc_users_voted table in table list, then click on the Structure button of this table and make sure all columns/fields exist in this table:

That's it! Don't forget delete all kind of caches again (plugin cache, CDN, minifier, optimizer). And refresh you browser pressing Ctrl+F5 to reset browser cache too.