Unfortunately, these items have a limited amount of energy. The remaining charge can always be seen while the item is working. After you run out of charge, the item turns into a decoration.
If you are convinced the item still has energy charges, make sure, that the path to the object is not blocked with other decorations, buildings or resource objects - clear obstacles off the path.
Also, make sure you placed a correct energy generator from the shopping cart, not a look-alike from one of the previous adventures.