I came across this sentence a while ago in the French subtitle for one of the episodes of the American TV drama Person of Interest.

I’m going to guess that its almost certainly a mangled translation of the phrase “Nobody has ever tried” or something similar. As everyone has repeatedly pointed out, the result is flat out ungrammatical in French.

The explanation is basically that English ever is a negative polarity item (it is overwhelmingly found in sentences featuring grammatical negation), but toujours in French is a positive polarity item with an even more restricted set of licensing contexts, meaning that while ever can appear in some affirmative contexts⁽¹⁾, it is practically impossible to construct a simple, grammatical negative sentence with toujours (other than when negating toujours itself, that is).

It is probably a safe bet that the “translator” was working off a dictionary and knew virtually no French at all, or the subtitles were outright thrown into an automated translator, because practically no competent French speaker could possibly come up with this sentence..

1. e.g. “If I ever […]”, “only ever”, the latter which I almost used in the parentheses.