Chastity in vanilla life discussion

Eventually, I persuaded my vanilla wife to take charge of the key. She handled it gracefully without many questions. We established some conditions, rules, limits, and punishments that felt within her comfort zone. Naturally, she isn’t a dominatrix nor does she have an innate dominance spirit, but she happily embraced the role. Since I already owned a cage that I had used willingly (which she knows), enduring being locked for those initial three days wasn’t too hard. However, on the third day’s end, she requested her pleasure. I attended to her body with delicious, extended foreplay and brought her to an orgasm via oral sex. Afterward, she handed me the key and asked that I remove my cage so we could have intercourse… without me ejaculating. As I took off the cage… Frustration. Immense frustration for me, which annoyed her too. My penis basically went soft. I felt frustrated because I wanted to provide something she understood about chastity but couldn’t manage it; I worried that by failing, she might think the game of chastity doesn’t offer her much pleasure after all, since when she unlocked me so we could connect… my erection withered! Is this normal? There must be a reason for this!