When the movie Star Wars premiered in 1977, it was both surprising and a revolution in its special effects. what is the correct parallel structure

Answer 1

I'd write it this way:

When the movie Star Wars premiered in 1977, its special effects were both surprising and revolutionary.

Do you see it?

Answer 2

it's incorrect It states to try again without using were I have revised this twice and it's telling me it's incorrect

Answer 3

Without using "were"? No verb in the sentence??