Now is an adverb that can mean "happening at or referring the present time or moment."
Now also has another meaning - here's Google's take on it:
- used, especially in conversation, to draw attention to a particular statement or point in a narrative.
"now, my first impulse was to run away"
This might be how now was intended to be used above. In this case, it will typically be used in the first word of the sentence and be offset with a comma. Since now would be being used as a "flag of importance" the tense of the verb it modifies wouldn't matter.