No fue culpa tuya; el error era del ordenador.

This is a very common question, because Spanish often switches between two past tenses where English just uses was.

• fue = preterite of ser
• era = imperfect of ser

In this sentence, the speaker is presenting the two ideas slightly differently:

• No fue culpa tuya: this treats the question of blame as a completed point or conclusion.
  
  • It wasn’t your fault.
• El error era del ordenador: this describes the error as belonging to / coming from the computer in the background situation.
  
  • The error was the computer’s / came from the computer.

A simple way to feel the difference:

• preterite often gives a finished fact, decision, or event
• imperfect often gives description, background, or an ongoing state

So the sentence sounds natural because:

• first clause = a clear verdict about blame
• second clause = an explanation of the situation

That said, tense choice can vary depending on context, but this combination is very natural.

Both are possible in Spanish, but culpa tuya is especially common in this kind of structure.

Spanish often uses:

• culpa mía
• culpa tuya
• culpa suya
• culpa nuestra, etc.

This uses the stressed possessive forms after the noun:

• mío / mía / míos / mías
• tuyo / tuya / tuyos / tuyas
• suyo / suya / suyos / suyas

Because culpa is feminine singular, you get tuya.

So:

• No fue culpa tuya = It wasn’t your fault
• No fue tu culpa = also possible, and also means It wasn’t your fault

The version with culpa tuya is very idiomatic and common.

Because it agrees with culpa, which is a feminine singular noun.

Agreement in Spanish works like this:

• culpa = feminine singular
• so the possessive must also be feminine singular
• therefore: tuya

Compare:

• el problema fue tuyo → problema is masculine
• la culpa fue tuya → culpa is feminine

So the ending is not about the person being spoken to; it is about the noun culpa.

Spanish often omits the article in this expression.

You will hear both:

• No fue culpa tuya
• No fue tu culpa
• No fue la culpa tuya → much less natural here

The most natural patterns are usually:

• ser culpa de alguien
• ser culpa mía / tuya / suya

So No fue culpa tuya is a standard, idiomatic way to say it.

If you add la, the sentence often becomes more emphatic or sounds less neutral, depending on context:

• La culpa no fue tuya = The fault wasn’t yours

That version is possible, but it is structured differently and feels more contrastive.

del is the contraction of:

• de + el = del

So:

• del ordenador = of the computer / from the computer

This contraction is mandatory in normal Spanish whenever de is followed by the masculine singular article el.

Examples:

• el libro del profesor = the teacher’s book
• el error del ordenador = the computer’s error

The only major exception is when El is part of a proper name, such as El Salvador:

• de El Salvador → not del Salvador

Because this is Spain Spanish.

In Spain, the usual word is:

• ordenador = computer

In much of Latin America, people more often say:

• computadora
• sometimes computador, depending on the country

So if you are learning Spanish from Spain, ordenador is exactly the expected word.

Not literally in the sense of real ownership. Here, ser de is being used to show where the responsibility or source lies.

So:

• el error era del ordenador

means something like:

• the error was the computer’s
• the error came from the computer
• the computer was responsible for the error

It is a natural way to shift blame away from the person and onto the machine.

It does not mean the computer consciously possessed the error. It just means the problem originated there.

Yes, you could, but it may sound slightly different.

• era del ordenador sounds more descriptive or explanatory
• fue del ordenador sounds more like a completed identification or conclusion

In many real conversations, both could be understood. But era often sounds smoother when you are giving background or explaining what the source of the problem was.

So in this sentence, era is a very natural choice.

Because the sentence is identifying blame or source, not location or temporary condition.

Spanish commonly uses ser for:

• identity
• origin
• possession
• responsibility

So:

• Fue culpa tuya
• Era del ordenador

both fit ser.

Using estar here would be wrong:

• No estuvo culpa tuya ❌
• El error estaba del ordenador ❌

Those do not work in Spanish.

Yes, but it is not exactly the same structure.

• No fue culpa tuya = It wasn’t your fault
• No fue por tu culpa = It didn’t happen because of you / It wasn’t due to your fault

The second version focuses more on cause using por.

So both are possible, but No fue culpa tuya is the more direct and idiomatic way to say It wasn’t your fault.

Yes. That would also be understandable and natural.

Compare:

• No fue culpa tuya → very idiomatic, common
• No fue tu culpa → also very common
• el error era del ordenador → slightly more descriptive/background-like
• el error fue del ordenador → more decisive or event-like

So your alternative sentence works, but the original has a slightly smoother rhythm and nuance.

Not especially for grammar. It mainly affects punctuation and style.

The semicolon connects two closely related ideas:

• No fue culpa tuya
• el error era del ordenador

You could also write:

• No fue culpa tuya. El error era del ordenador.
• No fue culpa tuya, el error era del ordenador.
  This is less ideal in careful writing, though people may still use a comma informally.

So the semicolon just shows a strong link between the two clauses while keeping them separate.

Yes, very natural.

No fue culpa tuya is a standard, reassuring phrase in Spanish. It is exactly the kind of thing you would say if someone feels bad about a mistake.

The second part, el error era del ordenador, explains why the person is not to blame.

So the full sentence sounds natural, supportive, and clear.