Have you set your X-Shopify-Storefront-Access-Token header?
You can get your token from {yourshop}.myshopify.com/admin/apps/private and selecting the private app and scrolling down to Storefront API and copying Storefront access token
Also ensure that the required permissions are set.
How are you trying to retrieve your products?
Just a couple of examples
Fetch
....
headers: {
"Content-Type": "application/json",
"X-Shopify-Storefront-Access-Token": "YourAccessToken"
},
....
If you are using GraphiQL - Select 'Edit HTTP Headers'
and add X-Shopify-Storefront-Access-Token in Header name and your access token in header value.
You can do the same with Postman by entering the values into the Header tab and sending the appropriate body by clicking on body, selecting raw then change the drop down value to JSON.
