Event Custom fields in certificate

Hi I am using the XML fields and need them to show in the certificate.
I tried [FIELD_SPEAKER] AND [SPEAKER] but these dont render anything see xml file below

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <fields name="params">
        <fieldset name="basic">
            <field name="field_speaker" type="text" label="Speaker" size="50" description=""></field>            
            <field name="field_hours" type="text" label="Number Hours" size="50" description=""></field>    
        </fieldset>            
    </fields>    
</config>

[FIELD_SPEAKER] and [FIELD_HOURS] tag should work. If not, you can submit a support ticket sending us super admin account of your site so that we can check it directly on your site for you

Regards,

Tuan