"CONNECTION PROBLEM There was a problem connecting with Steam. Please try again later"

[Frank]

Steam was working fine yesterday. Suddenly 12 hours ago and continuing now, I can't log into Steam. I can't play any of my games.
1. When I click on the Steam icon I first get the Sign In page.
2. I fill that in and press Sign In, then I get the message "CONNECTION PROBLEM There was a problem connecting with Steam. Please try again later".
I tried the first 3 fixes from here https://pcstrike.com/could-not-connect-to-steam-network/, Run as Administrator, and Change UDP to TCP, but no effect.
My setup is a Windows 10 PC, i7-67000K cpu, running in Australia.
Any suggestions?
Should I email [e-mail]?
Thanks.

[Frank]

Uninstalling and re-installing also worked for me.
Am now re-downloading all my games.
BTW, I couldn't make a backup using Steam because even though the Connection Problem error message say "Enter Offline Mode", that didn't work either, so I couldn't use the Steam Backup feature.
BTW 2, I tried emailing [e-mail], but as someone mentioned earlier this thread, that doesn't work, so I couldn't figure out how contact a live person at Steam for support.
This Connection Problem preventing Steam login was the worst Steam problem I have encountered in all my many years of using Steam.
I am now going to diversify my source of PC games and buy some games from other sources, so that if one service, such as Steam isn't working and is difficult to fix, I will still have games I can play from for example Epic store or GOG store.

[Pancakes11]

It was the worst problem I've seen on steam in my years here too. I still don't know what caused it considering it doesn't look like it affected many users (if it had this topic would have exploded)

[64kDroid]

I quickly fixed this by going into the Windows "Firewall & network protection" > "Add an app through the firewall" and removing any entry for Steam.

Open the app again and it'll work, and you'll need to accept the creation of the new firewall rule.

https://help.steampowered.com/en/faqs/view/6C09-ED6F-3A21-D2AB#security