I changed flights, dates, cities. Originally had certs applied to IND-MSP-CDG. They were waitlisted and then cleared. That trip was canceled so I changed to IND-VCE months later. The agent said she could not waitlist me for anything, since the cert had been used, but it was not a problem as long as I could find flights with immediate upgrade availability, which I did.
It sounds like your problem must be the proximity to your flight and maybe the fact that another carrier has taken over at the 24 hour window?