After the latest updates, I noticed that: if I use GPT via web or the “classic” app, I find the customization instructions I have always had inserted. In the new app with Chat and Codex, I don’t have any text in the “personalization” section. Why?
The new ChatGPT app currently doesn’t have the same personalization experience as ChatGPT Classic or the web version, so your existing customization instructions may not appear there yet. The experience isn’t fully unified across all apps right now.
For now, use ChatGPT Classic or the web version when you need those instructions applied. Hopefully the newer app catches up as the experiences become more consistent.