I can’t update my iCloud account

Hello sakib162

If you're getting an error message about a trusted certificate , take a look at the following article that can help. It provides the list of trusted certificates.

List of available trusted root certificates in iOS 15.1, iPadOS 15.1, macOS 12.1, tvOS 15.1, and watchOS 8.1 - Apple Support

Also, you stated that you cannot update your iCloud account. Are you trying to add more iCloud storage? If not, can you provide some more details? The more details you provide, it will be easier to get you pointed in the right direction.

Thanks for using Apple Support Communities.