Aflysningen af mødet kom for sent, så jeg var allerede på kontoret.

Because aflysningen is the definite form of the noun aflysning: the cancellation.

In Danish, definiteness is often shown by adding an ending to the noun instead of using a separate word like the:

• en aflysning = a cancellation
• aflysningen = the cancellation

So Aflysningen af mødet means the cancellation of the meeting.

Af here means of.

So:

• aflysningen = the cancellation
• af mødet = of the meeting

Together:

• Aflysningen af mødet = the cancellation of the meeting

This is a very common Danish pattern:

• åbningen af butikken = the opening of the shop
• slutningen af filmen = the end of the film

Because the sentence is referring to a specific meeting: the meeting, not just a meeting or meeting in general.

• et møde = a meeting
• mødet = the meeting

So:

• aflysningen af mødet = the cancellation of the meeting

If you said aflysningen af et møde, that would mean the cancellation of a meeting, which is less specific.

Yes, it is completely normal.

Literally, kom for sent means came too late, but in natural English here it means something like:

• arrived too late
• came too late
• was too late

So Aflysningen af mødet kom for sent means the cancellation notice happened too late for the speaker to avoid going in.

Danish often uses kom in cases where English might prefer something like arrived or came through.

For sent is the standard expression for too late.

• sent = late
• for sent = too late

Examples:

• Jeg kom for sent. = I arrived too late / I was late.
• Beskeden kom for sent. = The message came too late.

So in your sentence, the cancellation happened too late to be useful.

The subject is the whole noun phrase:

Aflysningen af mødet

That entire phrase means the cancellation of the meeting, and it is the thing that kom for sent.

So the structure is:

• Aflysningen af mødet = subject
• kom = verb
• for sent = adverbial phrase

Så means so in this sentence.

It links the first clause and the second clause:

• Aflysningen af mødet kom for sent = The cancellation of the meeting came too late
• så jeg var allerede på kontoret = so I was already at the office

So så shows a result:

The cancellation came too late, so I was already at the office.

Because så here is being used as a coordinating conjunction meaning so, and after that, Danish normally uses normal main-clause order:

• jeg = subject
• var = verb
• allerede = adverb

So:

• så jeg var allerede på kontoret

If så is used differently, especially as an adverb meaning then, you can get inversion:

• Så var jeg allerede på kontoret. = Then I was already at the office.

But in your sentence, så means so, connecting two clauses, so jeg var is the natural order.

Because in a normal main clause where the subject comes first, sentence adverbs like allerede usually come after the finite verb.

So:

• jeg var allerede på kontoret

Breakdown:

• jeg = subject
• var = finite verb
• allerede = adverb
• på kontoret = prepositional phrase

This placement is very typical in Danish:

• Jeg har allerede spist. = I have already eaten.
• Hun kommer sikkert senere. = She will probably come later.

Because Danish often uses på for places like workplaces, institutions, and locations where someone is present for a purpose.

So:

• på kontoret = at the office
• på skolen = at the school
• på hospitalet = at the hospital

I kontoret would usually sound wrong here. I is more often used for being physically inside something in a literal spatial sense, but with kontor, Danish normally says på kontoret when talking about being at work / at the office.

Because it describes a completed situation in the past.

The two past-tense verbs are:

• kom = past tense of komme
• var = past tense of være

So the sequence is:

1. The cancellation came too late.
2. As a result, the speaker was already at the office.

Both actions are viewed from a past point of time.

Yes. Aflysning is the noun form related to the verb at aflyse, which means to cancel.

So:

• at aflyse = to cancel
• en aflysning = a cancellation
• aflysningen = the cancellation

This is a useful word family to learn together.

Yes. A few natural alternatives are possible, depending on style.

For example:

• Mødet blev aflyst for sent, så jeg var allerede på kontoret.

  • The meeting was cancelled too late, so I was already at the office.

• Aflysningen kom for sent, så jeg var allerede på kontoret.

  • The cancellation came too late, so I was already at the office.

Your original sentence is completely correct, but some speakers might choose a shorter version if the meeting has already been established in context.