Upgraded to 2.3 now have cookie problems?

I just upgraded to 2.3 Friday I think… I could login one time after the upgrade, everything seemed fine until I made some minor text change. After that, I tried to login again, it wouldn’t let me.

The login screen keep saying my browser doesn’t support cookies.. which I know it is not true. I tested it on different computers and browsers, still no luck. Is it something to do with the new version?

Did I miss something during the install?

Also, before the upgrade, my subdomain works.. not it doesn’t work anymore, i have to go https://www.mysite.com/blog instead of blog.mysite.com.

Please help!!