После отмены заказа деньги вернулись не сразу.

Because после always requires the genitive case in Russian.

• отмена = nominative
• отмены = genitive

So:

• после отмены = after the cancellation

The same thing happens with заказ:

• заказа is also genitive

That is why после отмены заказа literally means after the cancellation of the order.

In this sentence, the phrase comes after после, so both nouns are affected by the structure:

• после
  • genitive
• отмена чего? → заказа in genitive as well

So:

• отмена заказа = cancellation of the order as a dictionary-style phrase or subject
• после отмены заказа = after the cancellation of the order

The first noun changes because of после, and the second noun stays in the form required by отмена.

In Russian, деньги (money) is grammatically a plural-only noun. Russian normally treats it as plural, even though in English money is singular.

So Russian says:

• деньги вернулись = literally the money returned
• not a singular form like деньга вернулась in normal modern usage

Because деньги is plural, the verb is also plural: вернулись.

Because the subject is деньги, and деньги is grammatically plural.

Russian past tense verbs agree with the subject in gender and number:

• вернулся = masculine singular
• вернулась = feminine singular
• вернулось = neuter singular
• вернулись = plural

Since деньги is plural, the correct form is вернулись.

Вернулись comes from вернуться, which means to return / to come back.

Here it is used in the sense:

• деньги вернулись = the money came back / was returned

The -сь / -ся ending often makes a verb intransitive or changes the focus:

• вернуть деньги = to return the money (someone returns it)
• деньги вернулись = the money came back / was returned (focus on the money)

So the reflexive form is natural when the money is treated as the thing that returned.

Yes, Деньги не вернулись сразу is also correct.

Russian word order is flexible, and changing it often changes focus rather than basic meaning.

Compare:

• После отмены заказа деньги вернулись не сразу.
  • emphasis on the whole situation after the cancellation, with not immediately at the end
• Деньги не вернулись сразу.
  • more direct: The money didn’t come back right away
• Не сразу вернулись деньги.
  • stronger emphasis on not immediately

In your sentence, putting не сразу at the end sounds natural and gives that idea a bit of emphasis.

Не сразу means not immediately, not right away, or not at once.

It does not usually mean never. It suggests that something happened, but only after some time.

So:

• деньги вернулись не сразу = the money did come back, but not immediately

This is different from:

• деньги не вернулись = the money did not come back

Russian often expresses ideas more directly and does not always use a passive construction where English might.

English might say:

• The money was not returned immediately

Russian very naturally says:

• деньги вернулись не сразу
• literally: the money returned not immediately

This is a common pattern. Russian often prefers an active or reflexive structure instead of a passive one.

Вернулись is the past tense of the perfective verb вернуться. Perfective aspect is used because the sentence talks about the result or completed event: at some point, the money came back.

The sentence is not about the process of returning, but about the fact that the return happened, though with delay.

Compare:

• возвращались / вернулись
• Деньги возвращались... = the money was in the process of being returned / kept coming back in some context
• Деньги вернулись... = the money returned (completed event)

So perfective is the natural choice here.

Yes, возвратились is possible, but вернулись sounds more everyday and natural in many contexts.

Compare:

• деньги вернулись = common, conversational
• деньги возвратились = more formal or bookish in some contexts

You might also hear:

• деньги не были возвращены сразу = the money were not returned immediately
• деньги сразу не вернули = they didn’t return the money right away

But for a neutral everyday sentence, деньги вернулись не сразу works very well.

Russian has no articles like the or a/an.

So:

• заказ can mean order, an order, or the order
• деньги can mean money or the money

The exact meaning comes from context. In this sentence, the context makes it clear that it means the order and the money related to that order.

It is not an idiom, but it is a very common and natural phrase built in a regular way:

• после = after
• отмена заказа = cancellation of the order

So после отмены заказа simply means after the order was cancelled / after the cancellation of the order.

You can build many similar phrases the same way:

• после оплаты заказа = after payment for the order
• после получения товара = after receiving the item
• после подтверждения заказа = after order confirmation

Yes. That is the normal implication.

Because it says:

• вернулись не сразу = returned, but not immediately

the usual meaning is that the money did eventually return.

If you wanted to say the money never came back, you would say something like:

• деньги не вернулись
• деньги так и не вернулись = the money never came back after all

So не сразу suggests delay, not failure.