I had the same experience when I called about it on Friday. First rep was very friendly and helpful but ultimately said she couldn't do anything (Got my Amex Plat 2/25, was informed the bonus expired 2/17. Amex cardmember for 12 years). Thanked her, hung up and called again, but before I even got through asking the rep said "I see another rep has already advised that you missed the cutoff." I was up front and told her that I thought I would try again and she said she certainly understood and that she sees I'm a longstanding cardmember but there was simply nothing they could do at this point, all the while apologetic. She suggested I write a letter to their PO Box in Fort Lauderdale if I wanted to push the issue. Again, thanked her for her time and hung up.

My last attempt after that was to send a secure message. Was declined within hours with a signature that specifically said "Manager, Fort Lauderdale FL," which seems to imply that the 2nd rep noted her suggestion in my file and also (reading between the lines here) tells me to give up.

My feeling is that once you've been declined for the bonus and your file indicates it, you're out of luck. Oh well, it was worth a shot!