Network error — could not validate coupon
Premium checkout could not reach the coupon validate API (premium.couponNetworkError). The code itself may still be valid.
Why this happens
Brief connectivity loss, API timeout, or site/API down — not the same as Coupon code is not valid (server rejected the code).
Diagnose and fix
1. Retry apply after refresh; check general site connectivity.
2. Admin: confirm checkout-coupon API is healthy (no 5xx in logs).
3. If validation works later with the same code, treat as transient.
4. If the server returns invalid/apply-failed, use those articles instead.