Can you post the full expression? Both functions are quiet simple, I haven't come across many issues with neither of the functions so far.
As per Qlik guide:
Now() ---- This function returns a timestamp of the current time from the system clock
Today() ---- This function returns the current date from the system clock.
try to use parameter inside function.(http://help.qlik.com/en-US/sense/November2017/Subsystems/Hub/Content/Scripting/DateAndTimeFunctions/now.htm)
Either 0, 1 or 2.
Returns the time when the last data load completed.
- When used in a visualization expression, this returns the time of the function call.
- When used in a data load script, this returns the time of the function call in the current data load.
Returns the time when the app was opened.