Labels can fail because the carrier service isn't available for the customer's country, the address isn't recognized, or the parcel is outside the service's size or weight limits.
You'll find each error message and how to fix it in Shipping label error troubleshooting, under "Carrier service not available" and "Errors you can fix yourself".
Quick checks
Service not valid for the country: check with your carrier or 3PL which service covers that country, then update the route's specifications under Settings > Carriers & Routes. See Carriers & Routes: how it works.
Address not recognized: check it in Google Maps and shorten Address line 1 to the standard street address, or use the nearest drop-off point's address. Then click Retry.
Postcode rejected: see Troubleshooting Shipping Label Error - Postal Code Rejection.
Still failing? Try creating the label in your carrier's own system. If that works, contact us with the order number and the full error message.