Does CSR not cover "Delayed Operational Reasons"?

I had a flight delay by over 24 hours in a connection city. The airlines (Frontier) tells me they do not provide letters of delay so I had to just send a screenshot from my email.

We were on our flight and deboarded because the pilot said it was a technical failure, but in email it says operational and change of aircraft and CSR denied my insurance claim. Am I doing something wrong? I am so confused.. I lost 2 days of class because of the delay and I was down over 300 dollars because of the delay. What even is going on with chase?