ZENDESK API Clients vs HTTP Requests/Responses

I'm working on a new web application in Node JS that needs to access Zendesk to check if there are tickets created for a specific user/requester e-mail (not agent e-mail).

I came accross two scenarios where I could use to make this request. The first one is recommended by Zendesk, which is access Zendesk using one of two API Clients available for Node JS. They are node-zendesk by Farrin Reid and Zendesk NodeJS API written by Adam Gray. Check it out here

The problem is that I am getting the message "Couldn't authenticate you" from Zendesk when I do the fetch. Maybe someone already came accross this problem and could help me out clarifying where exactly is my mistake or what I'm missing in the code.

I would appreciate a light on that.

Here is my code:

async function getZendeskTickets(clientEmail) {

    const zendeskAgent = 'agent@email.com'
    const api_token = 'some token'
    const query = `type:ticket requester:${clientEmail}`;
    const url = `https://mydomain.zendesk.com/api/v2/search.json?query=${query}`

    try {
        const res = await fetch(url, {
            method: 'GET',
            mode: 'no-cors',
            headers: {
                'Content-Type': 'application/json',
                Authorization: Buffer.from(`${zendeskAgent}/token:${api_token}`).toString('base64'),
            }
        })
        let data = await res.json();
        console.log('response', JSON.parse(JSON.stringify(data)))
    } catch (error) {
        console.log('zendesk response error', error)
    }

    return
}