Hi there Nathangaw! I have the same issue that you resolved it. How did you managed the rewrite of the URL and what was your domain configuration?
My setup is the following, an example:
example.es Main Domain
www.example.es Redirect to main domain and created cart the checkout page holds right here
Like:
www.example.es/123456789/checkout/123456789
But, when i create a checkout, the URL is:
example.myshopify.com/123456789/checkout/123456789
And when I try to rewrite it with the main domain, my app crashes because that route in Hydrogen is not configured. Thanks in advance!