Sign out of Gmail
If your Google service show "No access" after login cdnis.hk (Parent account),Please follow the step to logout parent account.
then install the 3rd party email receive app to login cdnis.hk account.
Depending on what device you use Gmail on, you can either sign out of Gmail, remove your Google Account, or switch between different accounts.
Sign out options
The only way to sign out of the Gmail app is to remove your entire account from your phone or tablet.
However, you can do many of the same tasks through other actions.
When you remove an account, it removes the account from all apps on the device. When your account is removed, you won’t be signed in to any Google products, like Maps or YouTube.
This option is good if you want to remove personal information from your device before you give it to someone else.
On your Android phone or tablet, open the Gmail app .
In the top right, tap your profile picture.
Tap Manage accounts on this device.
Choose your account.
At the bottom, tap Remove account.
Tip: Removing the account from your phone or tablet won't delete the account itself, so you'll still be able to use it on a computer or other devices.
Detail :https://support.google.com/mail/answer/8154?hl=en&co=GENIE.Platform%3DAndroid#zippy=%2Cremove-your-google-account-from-your-device