This is simply a CSS conflict. Please leave some example URL to allow us to debug and provide some solution for you.
In case you want to say thank you! 🙂 We'd really appreciate if you leave a good review on the plugin page. This is the best way to say thank you to this project and the support team.
Please navigate to Dashboard > wpDiscuz > Settings > Styles & Colors admin page, put the CSS code below in the "Custom CSS Code" textarea, save, it delete all caches and chgeck again, the issue should be solved:
In case you want to say thank you! 🙂 We'd really appreciate if you leave a good review on the plugin page. This is the best way to say thank you to this project and the support team.