Gmail not syncing

I have four gmail accounts in Apple Mail. One for my wife, One for my personal use, one for my private business use, and one for my business/staff communications. All work fine except for my personal account.

I have tried resetting it up in Apple mail. I can log in directly with a web browser, but Apple mail says my password or username are incorrect, at least it is saying that it cannot connect to the server.

This has been going on for a couple of weeks. I have searched these discussions and have had no luck.

This is consistent across 4 computers. Home iMac, wife's macbook, my macbook pro, and my work iMac. Consistent in that all gmail accounts work except my personal one.

I hope someone can help me.

Thanks,