Thanks for the question.
Yes, you can absolutely do more than one novena for the same petition. More prayers do not undermine faith but instead give even more fuel for the cause. Think about petitioning your congressman to do some important act of legislation:
- Wouldn't you want him to hear the plea from many sources?
More advocacy only helps the cause. Certainly novenas focus our prayer requests and show a willingness to sacrifice for the petition, but they are not magical, despite the fact that many hold that novenas are guaranteed to grant your desired petition. We have to become careful about not becoming superstitious in that regard.
God will always act according to His Will, and not contrary to it, so a novena that petitions God for something He does not desire, will not have the outcome one would expect or hope for, though I believe God does answer every prayer.
So, pray on, and God will use those prayers for the right result.