I’ve since create a brand new gmail account, specifically for handling mail.
I set the security requirement lower and it seems to work and it now forwards mail to my personal proton mail account.
The lower security settings may of helped, but I’m not sure
Which Lower Security Settings do you mean? The “Allow Less Secure Apps”? That’s one way to get SMTP access, the other is to enable 2FA and use an App Specific Password. As far as I know, you don’t need to do the Less Secure Apps stuff if you use 2FA.