I wouldn't use feeding response as an indicator, as most of my females eat better than my males. You have tried popping it...maybe you are too close to the cloaca with your low thumb? Try sliding your low thumb lower down the tail, and then doing a combination of rolling and sliding up towards to cloaca to try and evert the hemipenes. Right now you may be directly on top of them so they won't evert?

JonV