Each request for an Italy detail reports a 404. 

Even specifying country “it” and language “it”, it seems the API search for an ES property.
Ex: trying for https://www.idealista.it/immobile/29000541/ the output is

{“message”:“ad not found”,“httpStatus”:404,“ad”:{“adid”:29000541,“operation”:“sale”,“propertyType”:“homes”,“locationId”:“0-EU-ES-28-04-009-161-02”,“lastDeactivationDate”:1449141236000,“deactivationReason”:“user”,“tracking”:{“unsubscriptionId”:5,“isSuitableForRecommended”:true,“stateCode”:“A”,“commercialDataId”:130163688},“allowsRecommendation”:true,“contactInfo”:{“commercialName”:“Tus Alquileres & Su Venta”,“phone1”:{“phoneNumber”:“825760021”,“formattedPhone”:“825 76 00 21”,“prefix”:“34”,“phoneNumberForMobileDialing”:"+34825760021",“nationalNumber”:true,“formattedPhoneWithPrefix”:"+34 825 76 00 21"},“contactName”:“Tus Alquileres & Su Venta”,“externalReference”:“5201”,“userType”:“professional”,“agencyLogo”:“https://st3.idealista.com/8c/ed/d6/tus-alquileres-su-venta.gif",“contactMethod”:“all”,“micrositeShortName”:“tus-alquileres-su-venta”,“address”:{“streetName”:"calle greco”,“streetNumber”:4,“locationName”:“Seseña”,“postalCode”:“45224”},“agentInfo”:{“name”:"Tus Alquileres & Su Venta ",“proAgent”:false},“inVirtualMicrosite”:false,“corporatePhrase”:{“text”:“Affitto Acquisto Vendita Mutui 100% Appartamenti Ville Attici Case Case Seseña Viejo Quiñon Seseña Nuovo”,“autoTranslated”:true},“professional”:true}}}