You should never go to a id.fedoraproject.org link like that directly. Thats only something you get redirected to as part of a login flow... the transaction will need to be the exact one you are attempting.
So, it's expected that won't work.

On the testdays login failure, what exact error message(s) do you get?

I did not go directly: I clicked on the link (with the token) that appeared in my terminal generated by the runtests.sh of the kernel-tests after they finished in my laptop as instructed by https://fedoraproject.org/wiki/Test_Day:2025-08-10_Kernel_6.16_Test_Week

When this did not work, I tried to login here
https://testdays.fedoraproject.org/testday/1
as instructed by https://fedoramagazine.org/kernel-6-16-test-week-august-10-16/

There was simply no way to submit these results.
What else is needed from me to make this work?

Can you get a screenshot of the screen when you fail to login? or copy and paste the errors you get?

it's difficult for me to see where to look when I don't know what the errors you are seeing are.

i will provide this, need to run the tests again for that, but is there no log of failed logins by the user pdchris on that server?

The error was "authentication failure"

Now i can login here:
https://testdays.fedoraproject.org/testday/1
(yesterday it failed 5/5 times)

Is there a way to submit results on this page, or is it a list of results submitted over the id.fedoraproject.org link that is generated by runtests.sh?

Strange. I can look for any issues yesterday, but I wasn't aware of any. :(

Yes, if you are logged in there should be a "+" sign thing which goes to a 'submit result' link...

Thank you, I have just entered the results there.
I will run the runtests.sh again and try over the flow as well and keep you posted.
It may take some time because I am traveling right now and my internet is unstable

OK, I have re-run the tests now, the behavior was different:
1. after the tests were finished I got a similar message in the terminal as previously (attached screenshot: Kernel test results Screenshot_20250814_063210.png)
2. when I clicked on the link my browser (floorp) opened a new tab and directly changed to "You can close this window and return to the CLI" with address "http://localhost:12345/?code=3efd18fe-d6e7-443c-b37c-4840a4e74e02_SrACF56DBsneCle9FOoCq67qxElBPx7o" but name of the tab "id.fedoraproject.org....." (attached screenshot: Submission Screenshot_20250814_063539.png)
3. in the terminal new content appeared (attached screenshot: Submission terminal Screenshot_20250814_063539.png)

Questions:
1. was the submission now OK?
2. If yes: I assume I did not even see a login screen because I was already logged in in pagure.io because of this ticket and the browser picked up the login details?
3. But still, why did the address in the browser change to http://localhost:12345/?code=3efd18fe-d6e7-443c-b37c-4840a4e74e02_SrACF56DBsneCle9FOoCq67qxElBPx7o
4. and why was the 2FA with necessity for TOTP not a problem?
5. When I tried this a couple of days ago I received repeated authentication failures in both the address of the script and also in https://testdays.fedoraproject.org/testday/1, while now both worked directly. Could it be that my just (only 1 hour before) created Fedora account was simply not linked to these services yet?

In any case I am glad this works now.
Is this automatic submission / contribution documented anywhere I have access to?
Thank you

Yeah, so it uses the browser there to get an openidc token for you to use. If you were logged in/already had a token it would just use that.
Openidc redirects you when you authenticate, normally to an application, but in this case since the thing was command line, it just redirected you to localhost.

I'm glad it's working for you now.

Shall we close this issue out?

Yes, you can close the issue, thank you.
For others who may have similar peoblems: it seems Fedora infrastructure needs some hours to pick newly created accounts, and therefore I could not login in various servers soon after creation of a new Fedora account (but it worked flawlessly on the next day). A note about this in pertinent instructions (e.g. here: https://fedoramagazine.org/kernel-6-16-test-week-august-10-16/) could save some time and spare some frustration for new users.
Anyway, I am grateful it works now and glad to be part of the community.