window is not defined

Hi everyone, I am trying to call a backend function from client-side but I got this error :

"["Error loading web module backend/managePayments.jsw: window is not defined"]"

On this backend function, I am calling an NPM module that I previously installed :

import Fluidpay from 'fluidpay-js'
import wixSecretsBackend from 'wix-secrets-backend';

export function createPayment(amount, userEmail, cardInfo) {
 const fp = new Fluidpay({
        apiKey: wixSecretsBackend.getSecret("fluidPay_API_key"),
        environment: 'sandbox'
 })

Any idea on what might be the issue ?

Thanks !

Perhaps you will be able to find your answer in the FluidPay-API-Docs?
https://sandbox.fluidpay.com/docs/api/

or hereā€¦