Postman – collect variable

I’m new to Postman and using APIs but.. I’ve made a POST API call to get data:

[
    {
        "oha_c_2": "da7274da-2c3e-4197-994d-b3bcf89f73f0"
    }
]

I’m trying to save variable so I could use it in my next API call but it keeps saying variable is undefined.
This is the post-res script I use:

const response = pm.response.json();
console.log(response.oha_c_2);
pm.collectionVariables.set('reference', response.oha_c_2)

I’m sure it’s an easy fix for someone with some experience, any help is appreciated!