Wondering if this is for everyone or just me. Located Melbourne, Australia - when signing in I get an error 'server is currently unresponsive'. Checked firewall rules. Deleted them and reinstalled unity hub v2.1.2. No Joy.
Just checked the logs. It seems log in fails if access to adsrvr.org is blocked. As I work around I have temporarily added exceptions to access to insight.adsrvr.org and match.adsrvr.org
I had a similar warning in my logfile, but in my case the login page would just disappear instantly upon loading - never giving me a chance to attempt to login or see any error messages. Incase anyone else has the same problem, mine was caused by blocking the insight.adsrvr.org directly in my Windows\System32\drivers\etc\hosts file. Temporarily commenting out that line with a # finally let me login and download a free asset within the editor. If access to a tracking website is required to login (and thus use the asset store in 2019) then it needs to at least handle the error case of it being blocked a bit better. (Given the increased awareness about internet tracking nowadays, I'd imagine quite a few people have such websites blocked).
Sorry for the inconvenience. There was an issue with the sign-in page where the window was disappearing. It should be fixed as of yesterday.