"We are starting now."

Translation: On commence maintenant.

[ElizabethR553977]

The question posed is "WE are starting now", ergo the response should be in the same pronoun "WE" (nous). Yes, "WE" and "ON" are interchangeable However, either should be accepted in this connotation.

[DohiBalzs]

why "nous commence maintenant." not accepted?

[arielkangaroo]

Nous commençons maintenant.

Don't forget to conjugate verbs accordingly!