[Plugin: Multi-column Tag Map] Error when group numbers

When I set group numbers =yes, I got this error

Fatal error: Cannot redeclare flatten() (previously declared in ..../public_html/wp-content/plugins/multi-column-tag-map/mctagmap.php:248) in ..../public_html/wp-content/plugins/multi-column-tag-map/mctagmap.php on line 248

For your info, previously I was using this plugin https://www.dagondesign.com/articles/multi-column-category-list-plugin-for-wordpress/ to index category. I already uninstall and removed the plugin.

https://www.ads-software.com/extend/plugins/multi-column-tag-map/