Why am I getting an invalid API key error in my shopping cart?

If you see an error message that reads ERROR: Invalid API key during checkout, the store key from Grandville Printing was entered incorrectly in WooCommerce’s settings.

To find the store key in Grandville Printing, click Stores → Edit (next to your store) → API. Copy the key under API Access.

In WooCommerce click WooCommerce → Settings → Integration tab, paste the key into the “Grandville Printing store API key” field and click Save.