Cannot add a gmail account as a POP account to Outlook Pro Plus 2021

I am trying to get my 6 email accounts into one inbox by having them all be POP accounts.  One of my oldest gmail accounts will not recognize my gmail password.  I've gone into my Gmail and enabled POP, saved it to no avail.  It will only add the account as an IMAP account which separates the inbox and defeats my purpose.  TIA for your assistance!