Make steam ticket, and read steam logs, why it is so, if you have one of them steam error codes this matter in whats wrong, we cant fix or undo steam user that have a blocking issue.

Then we as steam users here can help then its because of a bug only.

pc.
is that Steam flush cmd you did, ( google how to do )


have all pc update, this is not a joke ( we even seen a windows update in the past had steam login issue a long time ago then that happend in the past. )

Dont expect windows find anything, ( you are testing and make sure you dont have a issue with OS ) or should i say be lucky if you find something and it fix itself.

( google how to do )
DISM.exe /Online /Cleanup-Image /Restorehealth
SFC /Scannow
chkdsk c:
chkdsk d:
chkdsk e:
chkdsk f:
chkdsk g:
chkdsk h:

This is not about me being right this is it, this is your system, and you should have done this already.

Then you post things like this "I have tried everything," you also trigger a we can't help you.

We can say gl with reset windows and steam or try windows safeboot mode.

Start steam in offline mode, and test does this matter, ( i dont care if you have no internetconnection this is about you try figureout steam client do work in offline mode.

And all this is only a login issue with steam server issue, dont forget i did not solve it i just made sure its not a client issue but login issue only at steam server with your information.

Read GTA post here, i know its not same issue with steam client and yet they procedur is.

This is a authentocation issue, or steam or your login/pw has a issue with some thing.

You need to be a expert or has good logic with what this is, then client do work in offline mode .


ps.
and im sorry if this is to complicated, but i bet other helper with IT experience know exatly why test this matter, this can be said to steam support, why is there so many login issue atm.

i had with GTA login server , but precedur is the same. ( then offline mode is working then this is a login issue or right to do it, ) see this matter. ( rest is steam support issue why do you have a login issue.)