Can’t enter gmail password iOS 15.1

Welcome jl149,

Try removing the email account and adding it back again: Add an email account to your iPhone, iPad, or iPod touch - Apple Support

Go to Settings > Mail, then tap Accounts, select your Gmail account and then scroll down to 'Delete Account'.

How to set up your email account automatically

If you use an email provider like iCloud, Google, or Yahoo, Mail can automatically set up your email account with just your email address and password. Here's how:

1. Go to Settings > Mail, then tap Accounts.

2. Tap Add Account, then select your email provider.

3. Enter your email address and password.

4. If you see Next, tap Next and wait for Mail to verify your account.

5. If you see Save, tap Save.

If you don't see your email provider, tap Other to add your account manually.

If you continue to have issues, any problems signing in on the email provider's website?

Wishing you well, cheers.

As of May 30, Google no longer supports "Less secure app access", its now impossible to use the gmail SMTP server with just a username and password.

https://support.google.com/accounts/answer/6010255?hl=en

Do as destiny241 said, delete the account and add it back. When you add it back you will be presented with the same Google login box that you get when logging into other Google sites.