Hello andrew jobar,
Since the birth date is already correct, first check whether Microsoft still classifies the account as requiring parental consent:
- Sign in to the Microsoft account profile.
- If Parent or guardian consent is required appears, use an adult Microsoft account to provide consent.
- If the profile cannot be edited, the adult account that originally provided consent must open Manage child accounts, select the affected account, and choose Edit this child’s personal info.
After Microsoft recognizes the account correctly, sign out of Minecraft and sign back in. If only multiplayer remains blocked, that is another online-safety permission rather than the Microsoft account age itself.