Если валидатор снова не сработает, лучше показать билет водителю.

Because сработает is the perfective future form of сработать. In this sentence, the speaker means if the validator fails / doesn’t work (on this occasion) — a single completed event in the future.

• сработает = will work / will go through / will function successfully
• не сработает = won’t work / fails

By contrast, не срабатывает is imperfective present and usually means something like:

• isn’t working
• doesn’t work
• keeps failing

So here, since the sentence is about a possible future situation, не сработает is the natural choice.

In Russian, after если (if), you often use the same tense that the situation logically requires. If the condition refers to the future, Russian commonly uses the future:

• Если он придёт, я скажу ему.
• If he comes, I’ll tell him.

So:

• Если валидатор снова не сработает...
  = If the validator doesn’t work again...

This is different from English, where we usually say if it doesn’t work, not if it won’t work.

Literally, сработать is a very flexible verb meaning something like:

• to work
• to go off
• to function
• to succeed
• to trigger

In this sentence, with валидатор (validator, the ticket-scanning or card-reading machine), сработать means:

• to register properly
• to scan successfully
• to work as intended

So валидатор не сработает means the machine does not accept or register the ticket/card properly.

Russian often leaves out words that are understood from context.

Лучше показать билет водителю literally means something like:

• Better to show the ticket to the driver
• It’s better to show the ticket to the driver

This is a common Russian structure:

• лучше + infinitive

It gives advice in a general, impersonal way. The person who should do it is understood from context.

Compare:

• Лучше подождать. = It’s better to wait.
• Лучше спросить у водителя. = It’s better to ask the driver.

If you wanted to make the person explicit, you could say:

• Вам лучше показать билет водителю.
  = You’d better show the ticket to the driver.

Показать is the perfective verb, meaning to show as a single complete action.

Here the idea is:

• if the validator fails, do one specific action: show the ticket to the driver

That is why показать fits better.

Compare:

• показать = to show once, successfully, as a completed act
• показывать = to show repeatedly, habitually, or as an ongoing process

So лучше показать билет водителю means it’s better to show the ticket to the driver (once, now, in that situation).

Because билет is an inanimate masculine noun. For inanimate masculine nouns in the singular, the accusative is usually the same as the nominative.

• Nominative: билет
• Accusative: билет

Here билет is the direct object of показать, so it is in the accusative:

• показать билет = to show the ticket

If it were an animate masculine noun, the accusative would normally match the genitive instead.

Водителю is the dative singular of водитель (driver).

The dative is used for the recipient of something — the person to whom something is shown, given, said, etc.

So:

• показать билет водителю = to show the ticket to the driver

A few similar examples:

• дать книгу другу = to give a book to a friend
• сказать учителю = to say to the teacher
• помочь пассажиру = to help the passenger

Снова means again.

So the sentence implies that the validator has already failed once, or that repeated failure is possible:

• Если валидатор снова не сработает... = If the validator doesn’t work again...

Russian also has опять, which often also means again. In many situations, снова and опять can be close in meaning, though опять can sometimes sound more emotional or annoyed.

Yes. Russian word order is flexible, because grammatical relationships are mostly shown by endings rather than position.

The original sentence:

• Если валидатор снова не сработает, лучше показать билет водителю.

This is the most neutral and natural order.

But you could rearrange parts for emphasis, for example:

• Если снова не сработает валидатор, лучше показать билет водителю.
• Билет лучше показать водителю, если валидатор снова не сработает.

These are understandable, but the original version sounds the most straightforward for ordinary speech.

Russian can use если ..., то ... just like English if ..., then ..., but то is often omitted because it is not necessary.

So both are possible:

• Если валидатор снова не сработает, лучше показать билет водителю.
• Если валидатор снова не сработает, то лучше показать билет водителю.

The version without то is very normal and natural.

Historically and grammatically, лучше is the comparative form of хорошо (well) and is also used very often in impersonal advice constructions.

In practice, in this sentence, it functions like better in English:

• лучше показать = better to show

So you do not need to overthink the label too much. The important pattern is:

• лучше + infinitive = it’s better to ... / you’d better ...

Yes, it can sound like practical advice for a specific situation, but it can also be understood as a general instruction.

Depending on context, it may mean:

• If the validator fails again this time, show the ticket to the driver.
• If the validator doesn’t work again in such cases, it’s better to show the ticket to the driver.

Russian often allows this kind of slight ambiguity, just as English does. The surrounding context usually makes it clear whether it is about one event or a general recommendation.