This article explains why you can't change the email address associated with your Community Gaming account:
Changing the registered email address for a Community Gaming account is not possible because the email address is intricately linked to the CG blockchain wallet.Each CG wallet is uniquely identified by the associated email address. Losing access to or changing the email address would result in a loss of wallet access and any stored funds.
This linkage between the email address and wallet is essential for security and identity verification, safeguarding your assets and account information.