The error "Received Status code 401 while making a GET request to big cartel:" is due to incorrect Big Cartel login information, such as an incorrect username or password.
To resolve the error, follow the steps below.
Click the Settings tab.
Under eCommerce select eCommerce Integrations.
Select your Big Cartel integration from the list.
Update with the correct Big Cartel login information.
When finished click Save Changes.
Allow a few minutes to pass and the error will disappear and orders will start synchronizing again.