Have you rebooted your router to see if that fixes the issue?

"no connection with steam server"

Contact own ISP, i bet this use to work according to you.

And if yo have change nothing, then it look like a issue from you into steam or back from them.

ps.
Dont have change isp or router or security app, im sure you know why i post like this.

Check with a browssr can you login there, more a own pc wth a block port or app issue.
add steam.exe to exception rules in AV app ( antivirus app )

WIFIi and VPN , and no to proxy, try cable check browser settings or change default browser as test even.

Do it work on spare pc or friends laptop, you try proof this is own pc or not, ISP or steam in other end.

you can try reinstall steam over current even, and steam flush cmd ( google how to do. )
do note "no connection with steam server" i see that as a connection issue so technical all how should a flush cmd could fix this, yes im rough or judge very hard with the statement you, because my education on network has done such to ppl that read no connection.

we have seen other stema user say reinstall steam fix it or windows even, and something most be broken in windows then, i still stand on no connection. is not bendable, there is a reson stem tell you this.

feel free to check system ( google how to do )

DISM.exe /Online /Cleanup-Image /Restorehealth
SFC /Scannow
chkdsk c:
chkdsk d:
chkdsk e:


do not underestimate nx suggestion, if your ISP have change something.
but also seem wrong then other web site working, again what if your ISP and there partners partner have issue.

same too me
I've tried everything. Like you, this started happening suddenly on Friday evening. I've never had this problem before.

Web Steam access is fine, too.

This is a Steam server issue. How long do I have to wait?

Same to me . happening on friday evening only cilent , I can acces steam on brower and phone too

Try the following as well, one at a time:

▶ Go to Steam settings and under the Interface section, disable both "smooth scrolling in web views" and "GPU accelerated rendering in web views". This will require a restart. These settings, when enabled, have been known to cause issues with Steam to operate normally for some users. Occasionally, this affects certain users only after an update to Steam occurs.

▶ Check the "achievement_progress.json" file, and make sure its size is relatively small -- typically a few KBs. If not, then make a backup copy and delete the original. Steam will rebuild that with a newer, smaller file. If it doesn't help, then you can always return the backup copy.
-- The file can be found in your Steam installation directory under userdata/[usernumber]/config/librarycache.

▶ Clearing the download cache may help. Go to your Steam settings and under the Downloads section, click the "Clear Cache" button for Clear Download Cache. This deletes ongoing downloads and temp files from SteamApps and Workshop items. Hence, unfinished downloads will need to be restarted again from zero so be aware of that.

▶ Similarly, clearing the Steam cache in your AppData folder could help. Sometimes files simply go wonky like the above cases. Navigate to your AppData folder (which may be hidden), and nestled under Local and Steam, remove the files there after creating a backup as necessary.
For WIndows:
-- Windows key + R, then type "AppData" under the Run dialog box.
-- Found alternatively via: ...Users\[UserName]\AppData\Local\Steam, usually on your C drive.
-- For MacOS, it should be ~/Library/Application Support/Steam/

hey try this !
https://tars.tistory.com/335
download regestry file