Le rapport signale une défaillance.

In French, nouns usually need a determiner, such as an article.

• le rapport = the report
• French generally does not omit the article as often as English does.

So Le rapport signale une défaillance sounds natural, while bare rapport would usually be incomplete in a normal sentence.

Because rapport is a masculine noun in French, so it takes the masculine singular definite article le.

• le rapport
• not la rapport

This is something you normally just have to learn with the noun. A good habit is to memorize nouns with their article:

• le rapport
• la défaillance

Signale is the present tense of the verb signaler.

It is:

• il signale = it signals / it reports / it indicates

Since le rapport is third-person singular, the verb is also third-person singular:

• Le rapport signale ...

This present tense can often translate into natural English in more than one way depending on context:

• The report indicates ...
• The report reports ...
• The report notes ...

Because in French, the subject noun is already present: Le rapport.

French does not need an extra subject pronoun when the subject noun is explicitly stated.

So:

• Le rapport signale ... = The report indicates ...

You would only use a pronoun if you replaced the noun:

• Il signale une défaillance. = It indicates a failure.

Here il stands for le rapport.

It is related, but the meanings do not always match perfectly.

Signaler often means:

• to indicate
• to point out
• to report
• to flag

In a sentence like this, signale is often best understood as:

• indicates
• reports
• flags

So although English signal exists, French signaler is often broader in everyday and formal usage.

Because défaillance is a feminine singular noun, so it takes une in the indefinite singular.

• une défaillance = a failure / a malfunction / a defect, depending on context

Compare:

• un problème
• une défaillance

The article une corresponds to English a or an.

Not always. Défaillance is a fairly broad word and can mean different kinds of failure depending on context, such as:

• a technical failure
• a malfunction
• a breakdown
• a defect
• a lapse
• a weakness

In a report or technical context, it often suggests:

• a failure
• a malfunction
• a defect

So the exact English wording depends on what kind of report it is.

French accents are part of the correct spelling.

In défaillance, the é is important because it shows pronunciation and distinguishes the written form. You should write it as:

• défaillance

not:

• defaillance

Accents are not optional in standard French writing.

A careful approximate pronunciation is:

luh ra-por see-nyahl yoon day-fah-yahns

A more French-like IPA pronunciation is:

/lə ʁa.pɔʁ si.ɲal yn de.fa.jɑ̃s/

A few useful notes:

• Le is usually a light luh sound.
• The gn in signale sounds like ny in canyon.
• une has the French u sound, which does not exist exactly in English.
• The ending of défaillance is nasalized.

Because this is a very standard French sentence pattern:

Subject + Verb + Object

• Le rapport = subject
• signale = verb
• une défaillance = object

So French and English line up quite closely here, which makes this sentence easier than some others.

Usually no. This is a very important false-friend point.

In this sentence, rapport means:

• report

But English rapport usually means:

• a good relationship
• mutual understanding

That English idea is usually expressed differently in French, for example:

• de bonnes relations
• un bon contact
• sometimes un rapport in a different, more abstract sense, but not usually in the everyday English rapport sense

So in Le rapport signale une défaillance, rapport definitely means report.

Yes, very possibly.

Depending on context, these can be close:

• signaler = to report, flag, point out
• indiquer = to indicate
• mentionner = to mention

The choice depends on nuance:

• signaler often suggests drawing attention to something noteworthy
• indiquer is a bit more neutral
• mentionner means simply stating or mentioning it

So Le rapport indique une défaillance is grammatically fine, but it is not always exactly the same nuance.

They are:

• le rapport → les rapports
• une défaillance → des défaillances

So the whole sentence in the plural could become:

• Les rapports signalent des défaillances.

Notice the changes:

• le → les
• une → des
• signale → signalent

Even though signalent and signale are pronounced similarly in many contexts, the spelling changes to match the plural subject.