Learn Hardcore German: Die Mitarbeiterin konnte sich vorhin nicht einloggen, weil das Passwort falsch war. - The female staff member could not log in earlier because the password was wrong.

Because the time adverb vorhin (“earlier today”) puts the event in the past. With modal verbs like können, German commonly uses the simple past in speech: konnte = “could.”

Why do we need the reflexive sich with einloggen?

In standard German the verb is reflexive: sich einloggen (“to log oneself in”). For 3rd person singular, the reflexive pronoun is sich: Sie loggt sich ein. Using sie instead of sich would mean “she logs her (someone else) in,” which is different.

Is einloggen a separable verb? How does that affect word order?

Yes. Examples:

Present: Sie loggt sich ein.
Perfect: Sie hat sich eingeloggt.
With a modal: Sie konnte sich nicht einloggen.
With zu: sich einzuloggen (zu goes between prefix and stem).

Why is nicht placed before einloggen and after vorhin?

Nicht usually precedes the element it negates. Here it negates the verb phrase: nicht einloggen. Putting it before vorhin (… nicht vorhin einloggen) would negate the time (“not earlier”) rather than the action, which changes the meaning.

Why does the verb go to the end in weil das Passwort falsch war?

Weil is a subordinating conjunction; in such clauses the finite verb goes to the end: weil … war. In a main clause it’s Das Passwort war falsch. Note: colloquial speech sometimes uses verb-second after weil (e.g., weil das Passwort war falsch), but that’s non‑standard.

What exactly does vorhin mean, and how is it different from similar words?

vorhin: earlier today, a short while ago (but not just now).
eben/soeben: just this moment.
gerade: right now / just now (context-dependent).
vorher/zuvor: earlier/before (relative to another time, not necessarily today).
neulich/kürzlich: recently (days/weeks ago).

Could I use denn or da instead of weil?

Yes, with nuances:

denn is coordinating (no verb-final): …, denn das Passwort war falsch. Slightly more formal/written.
da is subordinating like weil, often used when the reason is assumed to be known: Da das Passwort falsch war, …

Can I say the simple past of the main verb, like loggte (sich … ein), instead of using konnte … einloggen?

It’s possible: Sie loggte sich vorhin nicht ein, but in everyday German the simple past of borrowed verbs like loggen sounds marked. More natural are either the perfect (Sie hat sich vorhin nicht eingeloggt) or a modal in the simple past (Sie konnte sich … nicht einloggen).

Why die Mitarbeiterin and not eine Mitarbeiterin?

Die points to a specific, known employee; eine would introduce an unspecified one. Also, Mitarbeiterin is explicitly female; for gender-neutral language you may see Mitarbeitende or forms like Mitarbeiter:innen.

Why das Passwort instead of ihr Passwort (“her password”)?

You could say ihr Passwort, but ihr is ambiguous in German (her/their/your-formal). Using das Passwort avoids that ambiguity and can sound more neutral or generic.

Must sich always be used with einloggen?

In standard usage, yes: sich einloggen. You may see einloggen without sich in some tech contexts or regionally, but the safest, most widely accepted form is reflexive. A common alternative is sich anmelden = “to log in” (not to be confused with sich registrieren = “to sign up”).

Is falsch the only option? What about nicht richtig, inkorrekt, or fehlerhaft?

falsch is the idiomatic choice for a wrong password. nicht richtig is fine but a bit softer. inkorrekt sounds formal/technical. fehlerhaft means “faulty/defective” and isn’t used for passwords.

Can I move vorhin to the front?

Yes: Vorhin konnte sich die Mitarbeiterin nicht einloggen, weil das Passwort falsch war. Fronting time adverbs is common to set the time frame as the topic.

Why not say a weil-clause with the modal, like …, weil sie sich vorhin nicht einloggen konnte?

That sentence is also correct, but it states the consequence (“because she couldn’t log in”) rather than the underlying cause (“because the password was wrong”). Your original gives the specific reason.

Why nicht here and not kein?

Use nicht to negate verbs, adjectives, or specific parts of the clause: sich nicht einloggen. Use kein to negate an indefinite noun: Sie hatte kein Passwort. Here we’re negating the action, so nicht is required.

Is sich accusative or dative in this sentence?

Accusative. Most reflexive verbs use accusative when there’s no other direct object: Sie loggt sich ein. Reflexive dative appears when an additional accusative object is present, e.g., Ich wasche mir (DAT) die Hände (AKK).