Not sure what to recommend. I'd be tempted to take it, but wanted to share my recent experience which might lean me towards requesting a refund if they made me this offer.
On March 10, I canceled a Frontier flight (for other reasons) and took a travel credit (they call it a "credit shell") because I was going to use it later in the summer. I was eligible since I was outside 60 days. Then I rebooked my May WDW trip on a different airline that had the days I wanted to go to FL since Frontier is limited service where I am and it was bringing us in at 1 a.m. for a weekend trip.
So I found another trip I wanted to take this summer and planned to use Frontier for that when our time is more flexible for their limited schedule. I've now been trying to use that credit to book August and every single time I try to use it I get an error message saying my code is not valid. Extensive online research seems to indicate I'm definitely using the right code.
I emailed them on 3/18 and they said it might take more than 10 days to respond on the auto-email I got. Still nothing, and can't call either, I called last night and the recording said 2-hour wait and they only want to talk to people flying within 72 hours. I totally understand that, but if they are going to limit time frame when customers have to rebook (my date is June 10, so I've got wiggle room) they should have a mechanism so customers can talk to someone to deal with errors on their website.
Although, I joined their Discount Den 10 days ago (not realizing I'd keep getting the credit shell error! ) so I could fly my youngest DD for free and they sent a $100 voucher for joining. THAT works when I tried to plug it in. It's the credit shells that aren't working, at least for me.
Unless I'm totally misunderstanding something?!? I haven't flown Frontier in a while and I can see on my account there is a credit shell, but it just won't apply to my payment
Edited to add:
@MarBee I missed your most recent post when I typed this
. Good luck and I hope you can get through!