Gmail not syncing on iPhone with POP accounts and two-factor authentication

My Gmail is not all coming thru to my iPhone. The emails are coming thru to my desktop Outlook.  I have checked the settings and everything looks good. I don’t have any filters and rules on. All of the accounts are setup as pop which I have been using for years. I had to delete the email from my phone since messages weren’t sending. They are sending now but not all of the are coming thru. I am using two factor authorization so I am using an app password.

[Re-Titled by Moderator]