Koden fungerar inte längre.

Because koden is the definite form of kod, meaning the code.

• en kod = a code
• koden = the code

Swedish often adds the definite ending to the noun itself, instead of using a separate word like the.

Fungerar is the present tense of fungera (to work, to function).

So literally:

• fungerar = works / is functioning

In this sentence, the present tense is used to express the current situation: the code does not work now.

In Swedish, fungera often means to work in the sense of to function properly.

So:

• Koden fungerar. = The code works.
• Det fungerar inte. = It doesn’t work.

This is very common for machines, systems, plans, methods, and also code.

In a normal main clause, Swedish usually places the finite verb in the second position, and inte often comes after it.

So the pattern here is:

• Koden = subject
• fungerar = finite verb
• inte längre = negation + time expression

That gives:

• Koden fungerar inte längre.

This is standard Swedish main-clause word order.

Inte längre means no longer or not anymore.

It expresses that something was true before, but is not true now.

So:

• Koden fungerar inte längre. = The code no longer works.
• also natural in English: The code doesn’t work anymore.

Using only inte would mean simply not:

• Koden fungerar inte. = The code doesn’t work.

But inte längre adds the idea of a change over time:

• Koden fungerar inte längre. = The code doesn’t work anymore / no longer works.

So längre is what gives the sense of anymore / no longer.

No. Längre can mean different things depending on context.

1. Comparative of long

   • en längre text = a longer text

2. In negative sentences, inte längre means no longer / not anymore

   • Jag bor inte där längre. = I don’t live there anymore.

So in your sentence, it is not talking about physical length. It is part of the fixed expression inte längre.

Yes. Funkar is a common, more informal spoken alternative to fungerar.

• Koden fungerar inte längre. = a bit more neutral/standard
• Koden funkar inte längre. = more informal, conversational

Both are very common and natural.

Yes. In a subordinate clause, inte usually comes before the verb.

Main clause:

• Koden fungerar inte längre.

Subordinate clause:

• Jag ser att koden inte längre fungerar.
  = I see that the code no longer works.

So this sentence shows main clause word order, but in subordinate clauses the negation moves.

A natural stress is often on inte längre, because that is the important new information:

• Koden fungerar inte längre.

If the contrast is especially important, längre may get strong stress, giving the sense of it used to work, but not now.

Yes, completely natural. It is a very normal way to say:

• The code no longer works
• The code doesn’t work anymore

It sounds idiomatic and would be very common in everyday conversation, technical discussion, or troubleshooting.