Claimed denied because of expired referral no one told me about

So I called my rheumatologist office yesterday to refill my meds and confirm my appointment (I go there every three months). Got told that I was no longer a patient because my referral expired. Weird, cause last year I got a 12 month referral and asked for the same thing this year. I called my primary care doctor and they confirmed it was expired, despite them asking for the 12 month one.

Here is the problem: my referral expired on August 15th, and my appointment with my rheumatologist was on August 17th!!! Literally no one told me that I got the 6 month referral instead of the 12 month I usually go for. Not my rheumatologist, who scheduled me 2 DAYS AFTER IT EXPIRED AND DIDNT SAY ANYTHING, nor my doctor, nor anyone.

Called my insurance and my claim was obviously denied. They said to call my doctor and extend the referral to see if it could be covered, but the agent sounded uncertain.

Anyone else has experienced this? What are my chances of it being covered after the referral extension? Or who to call to appeal the decision?

Florida Blue HMO is my insurance