Sort by price don't work

Hi, I’ve buyed the real estate theme and I set up a theme. I need to sort the listing by price, but this feature don’t work. The price is with commas, but I write correct. How Can I fix for make it work? My demo site is:

An example is:

https://sitodiprova.beppeweb.it/studio/?s=&listtype–1=Vendita&tx_comune=0&tipologia–3=&descrizione–4=&advanced_search=yes

The search resul is setted to price low high

Thanks
Giuseppe