Si no recordes la contrasenya, no pots obrir la carpeta ni l'arxiu.

Because they are two different words in Catalan:

• si = if
• sí = yes

So in Si no recordes la contrasenya..., si introduces the condition: if you don’t remember the password...

Recordes is the 2nd person singular present indicative of recordar:

• jo recordo = I remember
• tu recordes = you remember
• ell/ella recorda = he/she remembers

So si no recordes means if you don’t remember.

Catalan often leaves subject pronouns out because the verb ending already shows who the subject is.

Here, recordes and pots both clearly indicate tu:

• recordes = you remember
• pots = you can

So Si no recordes... no pots... is completely natural. You could add tu for emphasis, but it is not necessary.

Yes, many speakers use a pronominal form in everyday Catalan, but in this sentence recordar is being used as a normal transitive verb: recordar alguna cosa = to remember something.

So:

• recordes la contrasenya = you remember the password

This is perfectly natural and standard.
A learner should be very comfortable with this pattern.

Yes. Contrasenya is a feminine singular noun, so it takes la:

• la contrasenya = the password

The article is used because we are talking about a specific password, not passwords in general.

Pots is from the verb poder, which means to be able to / can.

Its present forms include:

• jo puc = I can
• tu pots = you can
• ell/ella pot = he/she can

So no pots obrir means you can’t open.

Because after poder in Catalan, the next verb normally stays in the infinitive.

So:

• pots obrir = can open
• pots veure = can see
• pots entrar = can enter

This works much like English can + base verb.

The two clauses are separate:

• Si no recordes la contrasenya = if you don’t remember the password
• no pots obrir la carpeta ni l’arxiu = you can’t open the folder or the file

Each clause needs its own negation if it is negative.
So the second no is necessary.

Ni means nor, and in negative sentences it often corresponds to English or after not.

So:

• no pots obrir la carpeta ni l’arxiu

means something like:

• you can’t open the folder or the file
• more literally: you can open neither the folder nor the file

Catalan often uses ni to link things inside a negative sentence.

Yes, both patterns are possible.

The sentence you have uses:

• la carpeta ni l’arxiu

You may also see a more balanced version:

• no pots obrir ni la carpeta ni l’arxiu

Both are natural. The repeated ni ... ni ... makes the neither ... nor ... structure more explicit.

Because el becomes l’ before a vowel sound.

So:

• el + arxiu → l’arxiu

This is called elision. It works like this with many singular articles in Catalan.

Because this sentence expresses a real or general condition:

• If you don’t remember the password, you can’t open the folder or the file.

Catalan often uses present + present for situations that are generally true or true right now.

If the sentence were more hypothetical, Catalan would use different forms, for example:

• Si no recordessis la contrasenya, no podries obrir...
• If you didn’t remember the password, you wouldn’t be able to open...

Because the sentence begins with a conditional clause introduced by si:

• Si no recordes la contrasenya, ...

When that introductory clause comes first, a comma is normally used before the main clause.

You could also reverse the order:

• No pots obrir la carpeta ni l’arxiu si no recordes la contrasenya.

In that order, no comma is usually needed.