When you fetch rates or buy a UPS label in SKULabs, you may see an error like this:
UPS API Error: Missing or invalid shipper number
UPS returns this error when the UPS account number (shipper number) saved on your UPS carrier account in SKULabs is wrong, or is not linked to the UPS.com user that authorized SKULabs. It is common right after you open a new UPS account or connect a different account number.
How to fix "Missing or invalid shipper number"
Sign in to UPS.com with the same UPS.com user you used to authorize SKULabs.
Open your UPS profile and go to the accounts page (UPS calls it Account Summary or Manage Accounts, depending on your region).
Check that your UPS account number is listed. If it is not, choose Add an Account and link the account number to your UPS.com user. UPS may ask for details from a recent UPS invoice.
In SKULabs, go to Settings > Shipping > Carrier Accounts and open your UPS carrier account. Check that the Account number matches the number on UPS.com exactly.
Click Re-authorize and sign in to UPS.com with the user that now has access to that account number.
Try fetching rates again.
Tip: If several people manage your UPS account, make sure the UPS.com user that authorizes SKULabs is the one that has the account number linked to it.
Still seeing the error?
If the account number is linked on UPS.com and the error continues after re-authorizing, contact UPS to confirm the account is active and allowed to ship through the UPS API, then contact SKULabs support at support@skulabs.com.