Klikam link w przeglądarce, ale plik się nie otwiera.

Klikam is the 1st person singular present tense form of klikać, so it means I click / I am clicking.

• klikać = to click
• klikam = I click / I’m clicking
• klikasz = you click
• klika = he/she/it clicks

Polish dictionaries usually list the infinitive form, but in a sentence you normally need a conjugated form.

Here link is the direct object of klikam, so it is in the accusative case.
But for many masculine inanimate nouns, the accusative looks exactly like the nominative.

So:

• nominative: link
• accusative: link

That is why the form does not visibly change.

Both patterns can be heard:

• klikać link = to click a link
• klikać w link = to click on a link

In modern Polish, especially in computer/internet contexts, kliknąć/klikać link is very common and natural.

So klikam link is not a mistake. It is a normal way to say I click the link.

The preposition w here means in. After w in the meaning in, Polish usually uses the locative case.

• basic form: przeglądarka = browser
• locative after w: w przeglądarce = in the browser

So:

• w domu = in the house
• w szkole = at school / in school
• w przeglądarce = in the browser

Przeglądarka means browser, usually a web browser.

It comes from the verb przeglądać, which means to browse / to look through.

So w przeglądarce means in the browser.

In Polish, ale means but, and it normally introduces a new clause.
A comma is usually placed before ale.

So this is standard punctuation:

• Klikam link w przeglądarce, ale plik się nie otwiera.

This is similar to English, where a comma often appears before but joining two clauses.

Not really. In this sentence, się does not mean the file is consciously doing something to itself.
It is part of a very common Polish pattern that makes a verb sound more like:

• open in the sense of be opening
• won’t open
• does not open

So:

• otwierać = to open something
• otwierać się = to open / to be opening

Compare:

• Otwieram plik. = I am opening the file.
• Plik się otwiera. = The file is opening.

In English, we often just say the file doesn’t open, but in Polish się is very natural in this kind of sentence.

Because otwiera comes from the imperfective verb otwierać, and that is the natural choice here.

• otwierać = to open, be opening
• otworzyć = to open completely / to open once successfully

In Polish, perfective verbs like otworzyć do not have a true present tense. Their present-looking forms usually refer to the future.

So:

• plik się nie otwiera = the file is not opening / won’t open
• plik się nie otworzy = the file will not open

In this sentence, the speaker is describing a current problem, so nie otwiera się / się nie otwiera is the right idea.

In Polish, nie is usually written separately from finite verb forms.

So:

• nie otwiera
• nie klikam
• nie działa

This is normal Polish spelling.

A learner may notice that with some other words, especially some adjectives or nouns, nie can be written together, but with ordinary conjugated verbs it is written separately.

Because plik is the subject of the sentence, not the object.

In:

• Plik się nie otwiera.

the file is the thing that is failing to open, so plik stays in the nominative case.

That is different from sentences where negation affects a direct object. For example:

• Mam plik. = I have a file.
• Nie mam pliku. = I do not have a file.

There the object changes under negation, but in your sentence plik is the subject, so it remains plik.

Polish word order is fairly flexible, and several versions are possible.

Your sentence:

• Plik się nie otwiera.

is very natural.

You may also hear:

• Plik nie otwiera się.

This is also possible, though the rhythm and emphasis are a little different.
In everyday speech, się often appears early in the clause, so plik się nie otwiera sounds especially natural.

For learners, the safest version to remember is the one in the sentence you were given.

It can mean either, depending on context.

• Klikam link w przeglądarce, ale plik się nie otwiera.

can mean:

• I’m clicking the link now, but the file won’t open
• or more generally, when I click the link, the file doesn’t open

Polish present tense often covers both current action and general repeated action, just like English can.

Both klikać and otwierać are imperfective verbs.

That matters because imperfective verbs are used for:

• ongoing actions
• repeated actions
• general descriptions of what is happening

That fits this sentence perfectly:

• Klikam = I click / I’m clicking
• nie otwiera się = it isn’t opening / it doesn’t open

If you wanted to focus on a single completed click, Polish would more likely use a perfective verb such as kliknąć in another tense, for example:

• Kliknąłem link, ale plik się nie otworzył.
• I clicked the link, but the file didn’t open.

So the sentence you have sounds like a description of the situation as it is happening.