@etsyasianart USPS offers free pickup typically for premium services, like Priority Mail or Priority Mail Express, which qualify for free pickup.
USPS Ground Advantage service may not fall under the “premium” category USPS refers to, so the “+” symbol indicating premium services might not appear on Ground Advantage labels for this reason.
For pickups with this service, a fee may be involved which can be confirmed by reaching out to USPS support.