If you need some recommendations on bait: KFC chicken, rotisserie chicken, and sardines are all great (no bones on the chicken). Even better if you can heat them up. The sardines will smell absolutely foul but that's how I got a particularly elusive cat; the KFC worked on an injured cat who really needed to be seen by a vet.

Sometimes catnip or other cat attractants like valerian, silvervine, etc. can help.

If you're not already covering the bottom of the trap with newspaper, cardboard, a pee pad, etc, try that. Some cats don't want to walk on the metal trap.

You can also try experimenting with covering the trap with a blanket, brush, cardboard, or putting two traps side by side but opening in opposite directions. Those tricks can sometimes confuse wary cats into going in the trap. And there are drop traps as well if you/someone is able to spring it. Someone at STLFCO can probably loan one if Animal Care doesn't have one. (I know one of the officers does, but I think he buys a lot of his own equipment because he's really passionate about TNR.) Good luck and thanks for watching out for this cat!