Translation:We are waiting for an appropriate point in time.
I am confused as to the en on passend (en). I thought since you had the en on einen, it would be passende.
einen has an -en ending indicating gender/number/case, so the adjective takes a weak ending.
The weak ending is -e in the nominative singular* and -en everywhere else (i.e. all cases in the plural and all non-nominative cases in the singular).
Since we have the accusative case here (not nominative), the weak ending is -en and so we have einen passenden Zeitpunkt.
* and the accusative singular for those genders where nominative = accusative, i.e. feminine and neuter, but not masculine.
What's wrong with "We are waiting for a fitting moment"? I realize it's not a literal translation, but it's as close as I can get to something that might actually be said in English, which "We are waiting for an appropriate point in time" would not be unless the speaker is a robot or something. (Native speakers would say "We're waiting for the right time", but I assumed Duo would as usual reject the idiomatic translation and therefore didn't bother to try it.)