Exegesis:

kai autoi ouden toutōn sunēkan ‘and they did not understand any of this.’ autoi refers to hoi dōdeka in v. 31 and is slightly emphatic. For suniēmi cf. on 2.50; it often refers to the understanding of a word or an action of Jesus.

kai ēn to rēma touto kekrummenon ap’ autōn ‘and this word was concealed from them,’ explaining the preceding clause: it was not their own fault that they did not understand Jesus’ word. The agent of the verb is not stated and this is here clearly intentional.

kai ouk eginōskon ta legomena ‘and they did not know his sayings,’ taking up and repeating in other words what was said in the first clause after the explanation given in the second. ta legomena is virtually equivalent to to rēma touto.

Translation:

They understood none of these things, cf. on 2.50.

This saying was hid from them, or, “the significance of the saying was hidden from them” (The Four Gospels – a New Translation), ‘this saying (or, what he said) was/remained obscure to them’ (cf. Willibrord); cf. also on “it was concealed from them” in 9.45.

And has consecutive force here, ‘so,’ ‘accordingly.’

They did not grasp what was said, synonymous with the first clause. Some renderings used are, “they did not know what Jesus was talking about” (Good News Translation), ‘the things spoken did not enter their attention/perception’ (Marathi), ‘they did not find the sense of that saying’ (cf. Uab Meto).

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.