The phrase "última vez recientemente" does not make sense in Spanish because the phrase does not contain a subject (all 3 words are adverbs). "Visto recientemente" is the literal translation of the same phrase but without "última" (last), as it flows better. For an extended version, see my second suggestion.

This is a proper wording of "Last seen recently", rearranged to more accurately flow as a direct response to the hypothetical question of "when was the last time this user was seen?". It is longer, however, which is why I first recommended the previous translation.