TRACE will print whatever the variable contains, if TRACE doesn't print anything, it means the variable evaluates to null.
What is the result of Max(data_esecuzione) if you only load that in the SQL part?
LOAD * SQL SELECT data_esecuzione FROM Table;
DBMs vary on how to deal with timestamps, if the value is not numeric, or not the value Qlik could expect, the Date() function will return a wrong value or it will be unable to interpret if it's a string value.
That will give you a hint on how to deal with the value on the Qlik side (the LOAD statement).