we were..- do you use main verb or etre plus past participle

Question

on n'etait pas supposé pouvoir venir vs on ne supposait pas pouvoir venir......"we were not supposed to be able to come"- I keep getting this kind of error- the first is correct, the second is what I tend to do- not sure if it is passive voice that I am missing, or if there are times when what I think is a verb is being treated like an adjective.  any help would be appreciated. thanks in advance.....

Accepted Answer

This is a matter of passive vs. active voice. 
"We were not supposed to come." In passive voice there's something being done to the subject (we) -- at least in a grammatical sense. And, there's always something or someone doing it, even though that might not be mentioned in the sentence. If it's missing, you can add it using "by such and such or so and so".
We were not being supposed to come (by your mom). -- I know this isn't proper English but it shows you the principle: it was your mom doing the supposing to us.
On n'était pas supposés... -- imperfect tense passive voice (we weren't supposed to...)On ne supposait pas... -- imperfect tense active voice (we didn't suppose....)

Answer

thank you for your help.  I see your responses frequently on this site, and appreciate the time you spend clarifying things for all of us

Answer

Thank you, Jill. Not being a native speaker, I don't get it right all the time either. But I'm happy you find it useful.