Please How to use code fences
Do you see errors in openhab.log or in VSCode?
Does the Channel for the Temperature show that it needs a Number Item or a Number:Temperature?
Is the sitemap named “termosifoni.sitemap”?
Where did you place the .items file and .sitemap?
In both the Item label and the sitemap label, you have suppressed showing the actual temperature. See Items | openHAB. When you define the label in both places, the label definition in the sitemap will take precedence.