Hi there!

Sorry for your issue.

Please use the following code in your custom CSS:

select.sppb-form-control:not([size]):not([multiple]) {
    height: auto;
}

Hope this will solve the issue for you!

Note: Path towards custom CSS(Joomla 3): Extensions>Templates>Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.

Best Regards