Он промахнулся снова.

• Он = he
• промахнулся = missed / failed to hit
• снова = again

So the sentence means He missed again.

The basic verb is промахнуться. The ending -ся is the reflexive particle.

In this verb, -ся is just part of the normal dictionary form; it does not mean that he literally missed himself. Many Russian verbs are simply used with -ся, and you have to learn them as whole verbs.

So:

• промахнуться = to miss, to fail to hit

Yes. Промахнулся is past tense.

Russian past tense is often built with -л-:

• промахнуться → промахнул-ся

This form means missed.

In Russian past tense, the verb agrees with the subject in gender and number.

Here:

• промахнулся = masculine singular
• промахнулась = feminine singular
• промахнулось = neuter singular
• промахнулись = plural

So Он промахнулся снова uses the masculine form because он means he.

The infinitive is промахнуться.

You might see these related forms:

• промахнуться = perfective, to miss (one completed miss)
• промахиваться / промахнуться? Actually the usual imperfective partner is промахиваться = to be missing / to miss repeatedly

In this sentence, промахнулся is from the perfective verb промахнуться.

Because the sentence talks about one completed event: he missed again.

Russian often uses the perfective for a single finished action:

• Он промахнулся снова. = He missed again.
  One more complete miss.

If you wanted a repeated or ongoing idea, you might use the imperfective:

• Он снова промахивался. = He kept missing again / he was missing again
  though this is less neutral in many everyday contexts.

So промахнулся is the natural choice for one more miss.

The stress is:

• промахну́лся
• сно́ва

A rough pronunciation:

• он прамах-NUL-sya SNO-va

The -лся cluster can feel tricky for English speakers. Try saying it slowly:

• про-мах-ну́л-ся

Yes. Он снова промахнулся is very natural, and many speakers would probably prefer that order.

Both are correct:

• Он промахнулся снова.
• Он снова промахнулся.

The difference is mostly about emphasis and style:

• Он снова промахнулся = neutral, common
• Он промахнулся снова = puts a little more focus on again

No. This is an important difference.

Промахнуться means:

• to miss a shot
• to fail to hit a target
• to miss in the sense of make a mistake in aiming

It does not mean to miss someone emotionally.

For I miss you, Russian uses a different construction:

• Я скучаю по тебе.

So:

• Он промахнулся снова = He missed again.
• not = He missed someone again.

It can be used both:

1. Literally: missing a target, a shot, a throw
2. More generally: making the wrong choice, being off the mark

Examples:

• Он промахнулся мимо цели. = He missed the target.
• С ответом он промахнулся. = He got the answer wrong / he missed the mark with his answer.

So the verb can be physical or figurative.

Because Russian can leave the target unstated if it is already understood from context.

Он промахнулся снова simply means:

• He missed again

English can do the same thing. You do not always have to say what he missed.

If you want to include more information, you can add context:

• Он снова промахнулся по цели.
• Он снова промахнулся при выстреле.

But without context, the short sentence is completely normal.

Yes. In many contexts, снова and опять both mean again.

So you can say:

• Он снова промахнулся.
• Он опять промахнулся.

A common learner note:

• опять is often a bit more conversational and can sometimes sound slightly more emotional, depending on tone.
• снова can sound a bit more neutral or bookish.

But in many everyday sentences, they are interchangeable.