Translation:I need Internet access to download this file.
Dlaczego "I need an internet access to download this file" jest źle? Czy ktoś zna zasadę używania "an" w takich sytuacjach?
"an internet access" is not correct English grammar. "Access" cannot be used with the indefinite article unless it is an adjective modifying a noun, e.g. "an access code". "An internet connection" on the other hand would be correct.
I put "an internet connection" and it was marked wrong. Is the word "dostęp" that specific?
That would be: „Potrzebuję połączenia z internetem, żeby pobrać ten plik” – obviously, in real life these are pretty synonymous, but on Duolingo, you are learning by example and that includes actual meaning of the words(like 'access'/„dostęp” here), so things have to be a bit more literal.
"I need internet access so that I can download this file" was not accepted.
While this makes a lot of sense, we stick to the literal translations as far as they are correct and natural, and you added the "so that I can" part, which was not in the Polish sentence.
I put "I need access to the internet to be able to access this file". Can this be added?