Can you provide a screenshot showing the parameter settings for your keys operation? There's an option called "mode" where you would need to determine what type of mode you are using for the parameter. For what you have below, I'd actually set that mode to "code expression".
Alternatively, you could use the "Set Variable Value" operation to create a local variable to your keyword test and, in the "Value" parameter for that, again, select code expression.
In both of the above cases, your code expression should be as follows... you are implying that you're running the code and taking the result and using it as the value.
aqConvert.DateTimeToFormatStr(aqDateTime.Now(), '%m/%d/%Y %H:%M')
Note that I added another parameter to the code... the DateTimeToFormatStr requires a parameter to indicate how you're formatting the string.