Hello @abezun,
This is typically caused by WordPress themes or custom code overriding the default styling of the select fields.
In order to provide you with the necessary CSS, we would need to review the source code of your site and see what exactly is overriding it.
You can submit a support ticket here with a URL to your WordPress site utilizing Advanced Sermons: https://wpcodeus.com/support/
Best regards,
Kevin Wilgenbusch