Are you not receiving emails or not able to send one?
Have you configured POP3 or IMAP
Not working is a very broad term. Refer to google article below...
Sync your Google Account with Apple apps
To sync content from your Google Account with the Apple apps on your device:
- On your iPhone or iPad, open the Settings app.
- Select Passwords & Accounts Add Account Google.
- Follow the steps to enter your email address and password. (If you don't have the latest operating system for your iPhone or iPad and you use 2-Step Verification, enter an app passwordinstead of your regular password.)
- Choose the content you'd like to add, then select Save.
The Google Account data you choose will sync with your iPhone or iPad. To see your content, open the corresponding app.