yóuyú kuāndài duànwǎng le, yīncǐ jìshùrényuán jīntiān huì lái.

Yes, they work together as a cause → result pair.

• 由于 introduces the cause: 由于宽带断网了 = because the broadband is down
• 因此 introduces the result: 因此技术人员今天会来 = therefore the technician(s) will come today

This pairing is fairly formal and very clear in written Chinese.

You can think of it like:

• 由于 X，因此 Y = Because of X, therefore Y

In English, using both because and therefore in one sentence can sound heavy, but in Chinese this pattern is normal, especially in formal writing.

Yes.

All of these are possible:

• 由于宽带断网了，技术人员今天会来。
• 宽带断网了，因此技术人员今天会来。
• 因为宽带断网了，所以技术人员今天会来。
• 宽带断网了，技术人员今天会来。

Using both 由于 and 因此 makes the relationship especially explicit and a bit more formal.

Both can introduce a cause, but 由于 is usually more formal than 因为.

• 因为 is very common in everyday speech.
• 由于 is more common in formal speech, writing, announcements, reports, and explanations.

So:

• 因为宽带断网了，所以技术人员今天会来。
  more conversational
• 由于宽带断网了，因此技术人员今天会来。
  more formal / written

They are similar, but 因此 is generally more formal and more written than 所以.

• 所以 = very common in spoken Mandarin
• 因此 = more formal, more literary, more common in written explanations

So this sentence sounds a bit more formal because it uses 由于…因此… rather than 因为…所以…

It means the broadband internet connection has gone down / been cut off.

Breakdown:

• 宽带 = broadband internet
• 断网 = to lose internet connection / to be disconnected from the internet
• 了 = marks a new situation or change of state here

So 宽带断网了 is not literally saying the broadband broke into pieces. It means:

• the internet is down
• the broadband connection has failed
• the network got disconnected

In natural English, you might translate it as:

• The broadband is down
• The internet connection is out

Here, 断网 functions like a verb phrase meaning to lose internet connection or to be offline.

So in:

• 宽带断网了

宽带 is the thing affected, and 断网 describes what happened to it.

In everyday use, 断网 is very common and can behave quite flexibly:

• 家里断网了。 = The internet at home is down.
• 突然断网了。 = The internet suddenly cut out.

Here, 了 marks a change of state or a newly relevant situation.

• 宽带断网了 = the broadband has gone down / is now down

It does not necessarily mean past tense in the English sense. Instead, it often signals that something has happened and the resulting state now matters.

Compare:

• 宽带断网。
  sounds incomplete or like a dictionary-style phrase
• 宽带断网了。
  the broadband has gone down; that is now the situation

So the 了 helps show that this outage has occurred and is the reason for what follows.

Chinese often leaves out subjects when they are obvious from context.

In this sentence, the important information is:

• cause: the broadband is down
• result: the technicians will come today

There is no need to say something like we or the company unless the speaker wants to emphasize who is involved.

This is very normal in Mandarin. Context often supplies the missing subject.

By itself, 技术人员 can mean:

• technical staff
• technician
• technicians

Chinese nouns usually do not have to show singular or plural clearly unless the speaker wants to.

So:

• 技术人员今天会来。
  could mean the technician will come today or the technical staff will come today

If you want to make one person explicit, you could say:

• 一位技术人员今天会来。

If you want to make several people explicit, you could say:

• 几位技术人员今天会来。

技术人员 is a broader term.

• 技术人员 = technical personnel / technician(s) / technical staff
• 工程师 = engineer

If the person coming is specifically an engineer, 工程师 would work. But if the speaker just means someone from technical support or a technician, 技术人员 is safer and more general.

So 技术人员 sounds like:

• someone from the technical department
• a service technician
• technical support staff

Here 会 most naturally means will.

• 技术人员今天会来。 = The technician(s) will come today.

In other contexts, 会 can also express probability, like is likely to, but in this sentence it usually sounds like a planned or expected future action.

So here the meaning is closer to:

• will come
• are coming today

rather than a weak might come

Chinese time words usually come before the verb phrase.

Basic pattern:

• Subject + time + modal/auxiliary + verb

So:

• 技术人员 今天 会 来
• technician(s) + today + will + come

This is very normal Chinese word order.

Other examples:

• 他明天会去。 = He will go tomorrow.
• 我们晚上要开会。 = We will have a meeting tonight.

Yes, that is possible.

For example:

• 今天，由于宽带断网了，因此技术人员会来。

This puts more focus on today as the time frame.

You could also say:

• 由于宽带断网了，技术人员今天会来。

Both are grammatical. The original version is very natural.

Yes, the comma helps separate the cause clause from the result clause:

• 由于宽带断网了，
• 因此技术人员今天会来。

In writing, this comma is very natural and makes the structure easier to read.

In speech, there would usually be a slight pause there too.

It can refer broadly to the broadband internet service/connection.

In real usage, 宽带断网了 does not force a strict technical distinction. It usually just means:

• the broadband internet is down
• the home/company internet connection is not working

So even though 宽带 literally refers to broadband, in context it often stands for the internet connection associated with it.

It is natural, but somewhat formal.

In everyday spoken Mandarin, many speakers would more likely say something like:

• 因为宽带断网了，所以技术人员今天会来。
• 宽带断网了，技术人员今天会来。
• 因为网络坏了，今天会有技术人员过来。

The original sentence sounds more like:

• a notice
• a customer service explanation
• a formal update
• written communication

So it is correct and natural, just a bit more formal than casual speech.