+0
.
These are both fine:

We need to investigate what it is that is blocking the server from connecting to other computers.
We need to investigate what is blocking the server from connecting to other computers.
.
Comments  
what it is that is blocking the server ... is an indirect question embedded in the full sentence.

This indirect question comes from a statement form:
It is [something] that is blocking the server ...

Substituting the question word gives:
It is [what???] that is blocking the server ...

Moving the question word to the beginning gives the indirect question form:
what it is that is blocking the server ...
___

The statement form shown above is called a cleft structure. It comes from the sentence:
[something] is blocking the server.

Use the search box to search for more information on the cleft structure, if you're interested.

CJ
MM and CJ,

Thanks.
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CJ,

I feel that, as per your explaination, the following sentence is not correct. Am I correct in that?

I am trying to understand what is the advantage of using trade weights as powers over...

Musicgoldthe following sentence is not correct. Am I correct in that?
Yes. The sentence is not correct. You are correct. The corrected version is:

I am trying to understand what the advantage is of using trade weights ...

Embedded indirect questions do not have an inversion of subject and verb. Direct questions have the inversion.

What is the advantage of ...?

But:

I don't understand what the advantage is of ....
I have only a vague idea of what the advantage is of ....
Can you guess what the advantage is of ...?
No one knows what the advantage is of ....
Until we can specify what the advantage is of ..., ....


CJ
CJ,

Thanks a lot. Wish you a happy and prosperous new year!
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