Could a language be reconstructed from a dictionary and lots of natural text?

You're asking three completely different questions between your title and the actual question.

1. The title is asking about reviving - this would mean making a dead language a live spoken language again. To that the answer would be a qualified yes. Look for instance at modern Hebrew. But that still requires some form of speech to be preserved.

2. The body is asking about:

a. Learning a language from texts and a dictionary. In that case, yes, it is possible for humans to learn a language in that way (at least the written part of it).

b. Learning a language for an alien from texts and a dictionary. The problem here is that a dictionary would not be of any use aliens unless it was a bilingual dictionary between their language and the human language. If it's just the dictionary of (say) English, then that's simply another text in English.

It would be possible to make sense of the texts for the aliens only if they could observe the context in which it is used. Simply seeing lots of texts is not enough without some external reference - as attested by the many undeciphered languages. This would be doubly hard since the Aliens would presumably not have the same script or maybe not even the same way of writing (phonetic vs syllabic vs ideographic).