To be on the same page is to be thinking or understanding an issue similarly, or in agreement, though not necessarily on every detail. It is usually said about efforts to solve a problem.

Knowyourphrase.com says the origin is may refer to students opening their textbooks to the same page, or choral singers opening their music. That sounds plausible but sometimes people simply make up good stories to explain a phrase.

If the phrase seems to be recent, so Know Your Phrase may have found the origin in 1974, in the Corona Daily Independent:

“I think we can beat Washington and whichever [football] team we play next to get into the Super Bowl. If 47 players and our coaches are all on the same page, we can do it.”

Wherever it came from, tweakyourbiz.com calls this a business cliché, “a handy crutch when you’re groping for a word in a pressurized situation.” Perhaps some original thinking would lead to fresh language.