Yes sometimes Prozac can cause insomnia in some people who take it.
I experienced insomnia myself and had a hard time sleeping when I was on Prozac before and after I was able to stop taking the Prozac I eventually was able to start sleeping again.
If you're taking Prozac and having trouble sleeping you should speak with your doctor and let them know about the insomnia as they can usually prescribe you a sedative medicine to take with the Prozac to help get rid of the insomnia.
That way you could still take the Prozac medication while still being able to sleep.
Sleep is very important to our health so if you're having trouble sleeping then getting on a sedative medicine can help with the insomnia.
If you're pregnant or plan to become pregnant you shouldn't take any Prozac during the pregnancy because taking Prozac during pregnancy can cause heart defects or serious lung problems in the baby.