Без кода подтверждения я не могу войти в личный кабинет.

Because без always takes the genitive case in Russian.

So:

• код = nominative, the basic dictionary form
• без кода = without a code, with код in the genitive singular

This is a very common pattern:

• без паспорта = without a passport
• без воды = without water
• без помощи = without help

So без кода is exactly what you should expect after без.

They are both genitive, but for different reasons.

• кода is genitive because it comes after без
• подтверждения is genitive because Russian often uses a second noun in the genitive to describe the first noun

So код подтверждения literally means something like code of confirmation, which English expresses as confirmation code.

Then when the whole phrase goes after без, you get:

• код подтверждения → base phrase
• без кода подтверждения → without a confirmation code

So only кода is changed by без directly. подтверждения is already genitive as part of the noun phrase.

Не могу means I cannot, I’m unable to, or I can’t.

It comes from the verb мочь = to be able / can.

• я могу = I can
• я не могу = I cannot

In this sentence, не могу войти means I can’t log in / I’m unable to log in.

This usually describes inability, not prohibition. So it is closer to:

• I’m not able to log in

than to:

• I’m not allowed to log in

This is about aspect.

• войти = perfective
• входить = imperfective

Russian uses the perfective here because logging in is seen as a single completed action with a result: either you successfully enter the account or you do not.

So:

• не могу войти = I can’t log in / I can’t get in

If you used входить, it would sound more like a repeated, habitual, or general process:

• Я не могу входить без кода подтверждения = I can’t log in without a confirmation code, as a general rule

That sentence is possible, but in a normal one-time situation, войти is more natural.

Yes. Literally, войти means to enter / to go in, but in digital and website contexts it is very commonly used for to log in or to sign in.

For example:

• войти в аккаунт = log into an account
• войти в систему = log into the system
• войти в личный кабинет = log into your personal account area

So this is a normal and natural use of войти.

Because after a verb of motion like войти, Russian uses в + accusative to show movement into something.

So:

• в личный кабинет = into the personal account area

Compare:

• в личном кабинете = in the personal account area

This is a very important contrast:

• в + accusative = direction, movement into
• в + prepositional = location, being inside

So here, since the meaning is enter/log into, в личный кабинет is correct.

Because кабинет is a masculine inanimate noun, and for masculine inanimate nouns, the accusative singular is the same as the nominative singular.

So:

• nominative: личный кабинет
• accusative: личный кабинет

Even though the form looks unchanged, it is still accusative because the verb and preposition require it.

You can see the case change more clearly with feminine nouns:

• в комнату = into the room
• в комнате = in the room

It usually does not mean a literal physical office here.

In modern Russian, especially on websites, apps, banks, and government portals, личный кабинет means something like:

• personal account
• account area
• user dashboard
• private account page

So it is a standard online-service term.

A very literal translation like personal cabinet sounds odd in English, but in Russian this phrase is completely normal.

Yes, very often.

Russian often omits subject pronouns when they are clear from the verb form. So you could also say:

• Без кода подтверждения не могу войти в личный кабинет.

That sounds natural in many situations.

Including я can add a little more clarity, contrast, or emphasis:

• Я не могу войти... = I can’t log in...

So both versions are possible.

No, Russian word order is fairly flexible.

This sentence starts with Без кода подтверждения to highlight the condition first: without the confirmation code...

Other possible orders include:

• Я не могу войти в личный кабинет без кода подтверждения.
• В личный кабинет я не могу войти без кода подтверждения.

These all mean roughly the same thing, but the emphasis changes.

• Starting with Без кода подтверждения emphasizes what is missing
• Starting with Я emphasizes the speaker
• Putting в личный кабинет earlier can emphasize the destination

Sometimes yes, especially in informal speech.

• войти is the more standard and neutral verb for log in
• зайти can also be used colloquially, especially in speech about apps, websites, or accounts

So:

• не могу войти в личный кабинет = standard, very natural
• не могу зайти в личный кабинет = also common in everyday speech

However, if you are learning the most standard phrasing for interfaces or formal Russian, войти is the safer choice.

Russian has no articles, so the sentence itself does not mark that distinction.

Без кода подтверждения can correspond to:

• without a confirmation code
• without the confirmation code
• sometimes even without confirmation code in a very technical style

English chooses a or the from context.

So this is not something Russian grammar shows directly. You learn to supply the article naturally when translating into English.

A helpful stress pattern is:

Без кóда подтверждéния я не могý войтú в лúчный кабинéт.

Approximate pronunciation:

bez KO-da pat-vyerzh-DYE-ni-ya ya ni ma-GOO vay-TEE v LEECH-ny ka-bi-NYET

A few useful notes:

• не могу is often pronounced closer to ни магу
• unstressed о often sounds more like a
• войти has stress on the last syllable: войтú
• кабинет has stress on the last syllable: кабинéт

If you want to sound natural, getting the stress right matters a lot.