Halo teman! Perhaps it could not fit well with "cannot", because the Indonesian sentence would need to use "tidak bisa". So, your sentence would be, for example:
Saya tidak bisa menemukan kabel di sana.
The Duolingo sentence could have many other translations in different tenses, using "a" / "the" with singular and plural nouns, and just needing the verb "find" in single or compound forms.
Selamat belajar! :)
In that case, how about 'I did not find a cable there'? You're much more likely to say that, even if the current sentence is no T technically incorrect.
It doesn't fit the Duolingo paradigm but it's possibly a more natural translation to English.
For me somehow "the cable" fits very naturally to this sentence, but I was marked wrong for it.