What should I do if my Slovenia Post parcel is lost or very late?

First confirm it is genuinely overdue rather than sitting in a normal scan gap or a customs hold. If it is truly late, contact Pošta Slovenije customer service with the tracking number, or ask the sender to open an inquiry, since the sender holds the postal contract and can file a search request or claim. For marketplace orders, the retailer's support can also re-check the handoff and reship.