How to get engagement in the ring

Me and my dog Hadrix do Barn Hunt with each other, and we had our first open trial this past weekend. He found both rats but refused to engage with me after finding them. He wanted nothing more than the rats and followed where they went with his eyes. I couldn’t get him to tunnel and barely got a climb. How do I work on this? I’ve already started making him work for every bit of kibble, but anything else to try?