You might try sliding the pan over to one of the places in her cage that she went in, in case she didn’t like the current spot it’s in. (I once moved the pan over about 4 inches, and Spockie slid it right back with his nose. I thought he didn’t have enough room. He disagreed.)
Another idea is to try separating the food from the pan. I’ve read that putting food near it encourages them to go as they eat, but she might be fussy and not care for her “dining room” to be right next to her “bathroom.”
Are the pans you’re using exactly the same? Also the litter in it? Same color? Could the cage one be harder to get into, or have a smell of something she doesn’t like (only known to a sensitive bunny nose)? Maybe her droppings aren’t masking it enough. Oh, another idea: put the one she uses now into the cage and swap the cage one out, so she’ll use it in the corner of your home where she’s used to going.