Do thiếu địa chỉ liên hệ nên phải đợi.

Do introduces a cause or reason. In this sentence, it means because of / due to.

A very common pattern is:

do + reason, nên + result
= because of X, so Y

So:

• Do thiếu địa chỉ liên hệ = because there is no contact address / because contact information is lacking
• nên phải đợi = so (someone) has to wait

This do ... nên ... structure is very common in Vietnamese.

It links a cause and a result.

Structure:

• do = because of
• nên = therefore / so

So the sentence is organized like this:

• Do thiếu địa chỉ liên hệ = cause
• nên phải đợi = result

In English, you might translate the logic as:

• Because there was no contact information, [we/they/he/she] had to wait.

In natural Vietnamese, sometimes one part is omitted if the meaning is clear:

• Do thiếu địa chỉ liên hệ, phải đợi.
• Thiếu địa chỉ liên hệ nên phải đợi.

All of these can work depending on style and context.

Thiếu means to lack, to be short of, or to be missing.

In this sentence, thiếu địa chỉ liên hệ means:

• contact information is missing
• there is no contact address/information available
• the needed contact details are lacking

A useful thing to notice is that Vietnamese often uses thiếu + noun very directly:

• thiếu tiền = lack money
• thiếu thời gian = lack time
• thiếu thông tin = lack information

So thiếu địa chỉ liên hệ is a very natural phrase.

Literally:

• địa chỉ = address
• liên hệ = contact / to contact

Together, địa chỉ liên hệ usually means contact address or more broadly contact information/details, depending on context.

In real usage, this could refer to:

• a mailing address
• an email address
• contact details for reaching someone

In some contexts, Vietnamese speakers might also say:

• thông tin liên hệ = contact information
• địa chỉ email = email address
• số điện thoại liên hệ = contact phone number

So địa chỉ liên hệ is understandable, though in some situations thông tin liên hệ may sound broader or more natural.

Vietnamese often leaves out the subject when it is already understood from context.

So Do thiếu địa chỉ liên hệ nên phải đợi does not explicitly say who had to wait. The subject could be:

• we
• they
• he/she
• the customer
• the company

It depends on the situation.

This is very normal in Vietnamese. If the speaker wants to be explicit, they could say:

• Do thiếu địa chỉ liên hệ nên tôi phải đợi. = Because there was no contact information, I had to wait.
• Do thiếu địa chỉ liên hệ nên chúng tôi phải đợi. = Because there was no contact information, we had to wait.

Phải means must, have to, or be forced/required to.

In this sentence:

• phải đợi = have to wait

It shows necessity or obligation caused by the situation.

So the meaning is not just waited, but had to wait.

Compare:

• đợi = wait
• phải đợi = have to wait

That small word adds an important meaning.

Both đợi and chờ can mean to wait.

In many situations, they are interchangeable:

• đợi tôi nhé = wait for me
• chờ tôi nhé = wait for me

However, there can be slight differences in tone or habit depending on region and context. In everyday speech, both are very common.

In this sentence, phải đợi sounds natural.
You could also hear:

• Do thiếu địa chỉ liên hệ nên phải chờ.

That would also be understandable and natural.

Vietnamese often puts the reason first and then the result.

So:

• Do thiếu địa chỉ liên hệ = because contact information was missing
• nên phải đợi = so had to wait

This is similar to English sentences like:

• Because there was no contact information, we had to wait.

Vietnamese does not need extra words like there was in the same way English does. It can be more compact.

So the Vietnamese structure is very direct:

• cause → result

Yes, it is understandable and basically natural.

However, depending on context, some speakers might prefer slightly different wording, such as:

• Do thiếu thông tin liên hệ nên phải đợi.
• Vì thiếu địa chỉ liên hệ nên phải đợi.
• Do không có địa chỉ liên hệ nên phải đợi.

These are all close in meaning.

A small nuance:

• thiếu địa chỉ liên hệ = lacking contact address/details
• không có địa chỉ liên hệ = there is no contact address/details

Sometimes không có sounds more straightforward if the information is completely absent.

Yes. Do and vì can both introduce a reason.

So you can say:

• Do thiếu địa chỉ liên hệ nên phải đợi.
• Vì thiếu địa chỉ liên hệ nên phải đợi.

Both mean roughly Because contact information was missing, [someone] had to wait.

Very roughly:

• vì is often the more common everyday word for because
• do can sound a bit more formal or written in some contexts

But both are very common and normal.

A comma is often used after the reason clause, especially in writing:

• Do thiếu địa chỉ liên hệ, nên phải đợi.
• Do thiếu địa chỉ liên hệ nên phải đợi.

In modern Vietnamese writing, people may or may not include the comma. The sentence is understandable either way.

Also, some writers omit nên if they already have do or vì:

• Do thiếu địa chỉ liên hệ, phải đợi.
• Vì thiếu địa chỉ liên hệ, phải đợi.

So punctuation and small function words can vary a bit.

Not directly. The sentence means the waiting happens because the contact address/information is missing.

So the logic is:

• missing contact information
• therefore, someone has to wait

If you wanted to say wait for the contact address, Vietnamese would need a different structure, for example:

• đợi địa chỉ liên hệ
• chờ thông tin liên hệ

In your sentence, thiếu địa chỉ liên hệ explains the reason, not the thing being waited for.

You can simply add the subject before phải đợi or earlier in the sentence.

Examples:

• Do thiếu địa chỉ liên hệ nên tôi phải đợi.
  = Because contact information was missing, I had to wait.

• Do thiếu địa chỉ liên hệ nên họ phải đợi.
  = Because contact information was missing, they had to wait.

• Do thiếu địa chỉ liên hệ nên khách hàng phải đợi.
  = Because contact information was missing, the customer had to wait.

Vietnamese is flexible, but this pattern is very common:

Do/Vì + reason + nên + subject + phải + verb

or, if the subject is already understood:

Do/Vì + reason + nên + phải + verb