How to fix Oauth error invalid_request in API development?

[BobCrisps]

Hi folks, I'd be very grateful please of some help.

I am developing an API in PHP using the shopify/shopify-api resource recommended by Shopify.

I am hosting the software to access the API on my own website.

I can get as far as generating a link to authenticate which looks like

https://[ME].myshopify.com/admin/oauth/authorize?client_id=[SOME_CHARS]&scope=read_all_orders&redirect_uri=https%3A%2F%2F[ME].myshopify.com%2Fdone&state=[SOME_CHARS]&grant_options%5B%5D=per-user

However when I click the link I get the error message: Oauth error invalid_request. The redirect_uri and application url must have matching hosts.

Please can you let me know what I'm doing wrong, many thanks