I would have thought there would be some, but I'd love some examples. So are there any languages in which the translation of 'knowledge'is not a mass noun?
Yes, it can in fact be plural in most European languages.
In French, Italian, German, Spanish, Russian et altri there are connaissances, conoscenze, Kenntnisse, conocimientos, знания... which are typically plural and translated into English as knowledge in many contexts.
Note that most Germanic and Latin languages have a distinction between connaitre and savoir. These words all share a root with the former, distinct from the root of wisdom, cognates and translations of which can also be countable in some of these languages.