My gmail quit working three days ago, all 5 Dahua cameras at exactly the same time (insecure app access allowed). Tried a brand new gmail, still doesn’t work. Tried the alternate port and ssl, still not. Tried app specific pass word and 2fa, still not. Tried rebooting camera and router, still not. Tried setting camera email to default and re-inputting account, still not. Tried logging in from web and mail app and the gmail accounts themselves have no issues. Tried the google page that says 'allow sign ins', didn’t work.
Tried yahoo and that works fine. I have contacted my isp but I think it's something google is doing given yahoo has no issues.