@milsou,

This is a result of hard caching and JS file minifying. Please make sure the forum page is excluded from all your caching and JS/CSS optimizing plugins. Then delete your browser cache.

More info: https://wpforo.com/community/faq/wpforo-and-cache-plugins/

I'd also recommend you disable all plugins, especially the cache and optimizer plugins, and test it again. This is a plugin conflict, for sure, and you should find the problem maker yourself.

It's ok for me... thanks a lot sir