Монетоприёмник то и дело не принимает монеты.

Монетоприёмник means coin acceptor or coin slot/mechanism that takes coins.

It is built from:

• монета = coin
• приём = acceptance, receiving
• -ник = a common noun-forming suffix for a device or thing associated with an action

So literally it is something like coin-receiver.

You will often see similar technical compound nouns in Russian.

То и дело is an idiomatic expression meaning:

• constantly
• repeatedly
• every now and then
• again and again

In this sentence, it suggests that the problem keeps happening: the coin acceptor keeps refusing coins.

It does not literally mean this and that matter here. As a fixed expression, it simply means repeated occurrence.

Because the sentence describes a habitual/repeated problem, not one single completed event.

So:

• не принимает = doesn’t accept / won’t accept / keeps not accepting
• it describes what the machine tends to do in general

If you wanted a one-time event in the past, you would use something else, for example:

• не принял монету = it didn’t accept the coin

Here, the present tense works like English doesn’t or keeps not when talking about repeated behavior.

Russian uses the imperfective here because the action is repeated, ongoing, or habitual.

• принимать = to accept, to be accepting, to accept repeatedly
• принять = to accept once, as a completed action

Since то и дело already suggests repetition, the imperfective is the natural choice:

• Монетоприёмник то и дело не принимает монеты.

A perfective form would sound wrong here if you mean a recurring problem.

This is a very good question, because Russian negation can affect case.

Here, монеты is the accusative plural of монета. For inanimate feminine plural nouns, accusative plural looks the same as nominative plural:

• монеты

So the sentence is using the normal direct object:

• принимать монеты = to accept coins
• не принимать монеты = not to accept coins

You may also sometimes see genitive under negation:

• не принимает монет

That version is possible too, but it can sound more bookish, more emphatic, or more like any coins at all / no coins. In everyday modern Russian, не принимает монеты is very natural.

Because it is the subject of the sentence — the thing performing the action.

The structure is:

• Монетоприёмник = the coin acceptor
• не принимает = does not accept
• монеты = coins

So монетоприёмник is in the nominative singular because it is the grammatical subject.

That placement is very natural in Russian.

The sentence structure is:

• Монетоприёмник
• то и дело
• не принимает монеты

Putting то и дело before the verb helps modify the verbal idea directly: the machine keeps failing to accept coins.

You could sometimes move adverbial expressions around in Russian, but this position is very normal and idiomatic.

It is pronounced approximately:

ma-nye-ta-pri-YOM-neek

The letter ё always indicates:

• the sound yo
• and usually the stress

So the stressed syllable is -ём-:

• монетоприёмник

In printed Russian, ё is sometimes replaced by е, but learners should remember that the correct pronunciation here is still приём, not прием with a plain e sound.

It is mostly neutral everyday Russian.

• монетоприёмник is a normal technical word
• не принимает монеты is completely standard
• то и дело is idiomatic and common, slightly conversational in flavor, but not strange or slangy

So the whole sentence sounds natural in ordinary speech and writing.

Yes, but the nuance changes a little.

Possible alternatives:

• Монетоприёмник постоянно не принимает монеты.
• Монетоприёмник всё время не принимает монеты.

Differences:

• то и дело = again and again, repeatedly, every so often
• постоянно = constantly
• всё время = all the time

То и дело often suggests repeated annoying recurrence rather than uninterrupted continuous failure. So in this sentence it is a good choice if the machine keeps refusing coins over and over.