Afhendingin seinkar stundum þegar rakningarnúmerið virkar ekki á vefsíðunni.

Because Icelandic usually puts the definite article the at the end of the noun.

• afhending = delivery
• afhendingin = the delivery

Here -in is the definite ending for this feminine noun in the nominative singular.

Seinkar is the 3rd person singular present form of að seinka.

In this sentence, it means something like:

• is delayed
• gets delayed
• is late

So Afhendingin seinkar is a natural Icelandic way to say that the delivery is delayed. Icelandic often uses a simple verb where English might prefer a passive expression like is delayed.

Because seinkar already carries the verbal meaning by itself. Icelandic does not need an extra is here.

English:

• The delivery is delayed

Icelandic:

• Afhendingin seinkar

So the meaning that English expresses with is delayed is packed into the single verb seinkar.

Stundum means sometimes.

Its position here is very natural:

• Afhendingin seinkar stundum

That is a neutral way to say The delivery is sometimes delayed. Icelandic adverbs can sometimes move around for emphasis, but this placement is common and straightforward.

Here þegar introduces a time clause, and in a sentence like this it can feel like when or whenever in English.

Because the sentence is about something that happens from time to time, English speakers may understand it as:

• when
• or more generally whenever

So the clause describes the situation in which the delay happens.

Because Icelandic forms compound nouns very freely.

Rakningarnúmerið can be broken down like this:

• rakning = tracking
• númer = number
• -ið = the for a neuter noun

So rakningarnúmerið means the tracking number.

The -ar- in the middle is a linking/genitive element that often appears in compounds. Long compound words are extremely common in Icelandic.

Virkar is the present tense of að virka, meaning to work or to function.

Icelandic does not rely on the English-style continuous tense as much. So:

• virkar ekki can mean doesn't work
• and in context it can also mean isn't working

A simple present form often covers both ideas.

Because in normal Icelandic sentence structure, ekki usually comes after the finite verb.

So:

• virkar ekki = does not work

That is the standard order. Moving ekki can happen for emphasis, but verb + ekki is the pattern learners should expect most often.

Because á means on here, and with location it takes the dative case.

The noun is:

• vefsíða = website / web page

After á in a location sense, it becomes dative singular definite:

• vefsíðunni = the website / the webpage in dative

So:

• á vefsíðunni = on the website

This is a good example of how Icelandic prepositions often affect case.

Yes, a little. This is a subordinate clause introduced by þegar.

In the clause:

• rakningarnúmerið = subject
• virkar = verb
• ekki = not
• á vefsíðunni = on the website

That order is normal after a conjunction like þegar. For an English speaker, it is helpful to notice that the structure is quite close to English here:

• when the tracking number doesn't work on the website

A useful quick guide is:

• þ sounds like th in thing
• ð usually sounds like th in this

So:

• þegar begins with the th sound from thing
• the ð in endings like -ið is softer, and in fast speech it may be less strongly pronounced than English speakers expect

You do not need perfect pronunciation immediately, but recognizing þ and ð early is very important in Icelandic.