Hi Shinehah,
We appreciate you reaching out to us. We understand that your Xcode does not automatically update even if "Automatically keep my Mac up to date" is enabled.
We’d like to gather additional details that may help us be in a better position to assist you.
How long have you been experiencing this issue?
Has it happened on multiple updates?
If the issue has just started, we recommend that boot into safe mode, then boot normally.
After trying that step, we recommend that you check if the issue persists.
How to use safe mode on your Mac
If the issue has been happening for quite some time or if you need further assistance, we recommend that you reach out to us through the support link below.
Xcode - Support - Apple Developer
Take care!