Missed flight And rebooking
 

Hi, I missed my one way flight out of Miami to NY. I already booked a new flight also on frontier from Fort Myers to NY but I was wondering if I would have to pay the 99$ cancellation fee once I check in at fort Myers.

The cancellation policy is here: Can I cancel my reservation? | Frontier Airlines
No, Frontier isn't going to charge you for missing the Miami to NYC flight, but you have the option of paying them $99 to get credit for the airfare you paid. You must use it within 90 days. If your original ticket cost less than $99 you obviously wouldn't want to cancel.