To connect your FedEx account, go to Shipping Options > Manage Carriers, click "Connect" next to FedEx and fill in the connection form.
You need an active FedEx business account. FedEx is strict about this form, so make sure every value matches your FedEx account exactly.
Account details (all required unless marked optional)
Invoice validation (US and Canada accounts)
FedEx validates your account with the details of your last FedEx invoice. Use an invoice issued within the last 90 days:
The FedEx End-User License Agreement box is checked by default. By connecting, you accept the agreement. Click "Connect".

Invoice information is incorrect. Check the invoice number, date and amount against your latest FedEx invoice. Enter the invoice number as 9 digits without dashes.
'account_number' must be 9 characters. Enter your FedEx account number as 9 digits, without dashes or spaces.