I got this email from F9, which may help you out...I was having the same problems too which were very frustrating...
"The EarlyReturns Customer Service Center will be closed and the web pages will be down
from 5:00 p.m. Friday, September 10th - Sunday, September 12th
while we upgrade our frequent flyer system.
We are very sorry for this temporary inconvenience; however, it will result in more stable and faster account access. We look forward to serving you when the site returns live and the EarlyReturns Customer Service Center reopens on Monday, September 13th.
*Please Note: Our general reservations center will be open and our Frontier website will be running during this time, so you may still access both of these to make reservations."
N674UW