username/pw invalid when setting up gmail account with Thunderbird

I know there's a lot of threads about this if you google the problem but none of those threads helped me.

I want to download the emails from gmail to Thunderbird so I want to use POP3 instead of IMAP which I've also selected.
I don't have two factor authentication for my gmail and I've checked that POP3 is allowed in my gmail settings.
I've also sudo ufw allow..

in 995/tcp
and..
out 465/tcp

and disabled and then enabled ufw afterwards but it didn't make any difference.