## Checkout: Pay button stays disabled after entering a valid Canadian postal code

**Severity:** S1 Critical  
**Priority:** P1 Urgent  
**How often:** Always (5 of 5 tries). Same on desktop Chrome. Works without the space (M5V3L9).

### Summary
Customers with Canadian addresses cannot complete checkout. Blocks all Canadian orders.

### Environment
- **Device and browser:** iPhone 15, iOS 27.0, Safari, 393x852
- **Page or screen:** https://shop.example.com/checkout
- **Environment:** production
- **Version or build:** 2.4.1
- **Account or role:** logged-in customer, wifi

### Before you start
Logged in as a customer with 1 item in the cart.

### Steps to reproduce
1. Open the checkout page.
2. Select Canada as the country.
3. Enter the address 100 King St W, Toronto, ON, M5V 3L9.
4. Fill in all other required fields.
5. Look at the Pay button.

### Expected result
The Pay button becomes active and the order total shows HST.

### Actual result
The Pay button stays disabled. No error message is shown. The console shows: 'Invalid ZIP code format'.

### Screenshots, video and logs
checkout-canada.mp4, console-error.png

### Workaround
Enter the postal code without the space.

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