The last state is the one that matters: it must not tell you whether an org exists.

Which org are you signing in to?

choosing among organizations — in October each person is in one organization (forge 34 §3.7)

You can belong to more than one, and they may not use the same way of signing in.

Either works. An org's short name goes straight there; an email address is a hint we look up. If your org gave you a link of its own, that link skips this screen entirely.
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Kordin Neo

Two orgs use that email domain

choosing among organizations — in October each person is in one organization (forge 34 §3.7)

acme.com is claimed by two orgs, so we are not going to pick one for you. Whichever you choose, you will be sent to that org's own way of signing in — they may not be the same.

Acme Labs Europe Signs in through the company directory. If you are staff, this is almost certainly the one. Acme Labs Signs in with an identity provider of its own. Separate org, separate people, separate everything.
Choosing wrong costs you nothing. You will be turned away at the other end rather than let into somewhere you do not belong, and you can come back here and pick the other one.
Kordin Neo

We cannot send you anywhere from that

choosing among organizations — in October each person is in one organization (forge 34 §3.7)

Nothing matched, and that does not mean the org does not exist. It might; it might be private; the name might be spelt differently. We are not going to tell you which, because this screen needs no credential to reach and answering it truthfully would turn it into a way of finding out who else uses this.

What actually helps. Ask whoever invited you for the link they used — an org's own sign-in link goes straight there and skips this entirely. Failing that, the exact short name, spelt as they spell it.
Try a different oneStart again
Kordin Neo