Question

Why did some of the delegates refuse to sign the constitution? social studies weekly 17?

Answer 1

They believed that there were flaws that needed to be addressed

This included both big issues like whether or not the bill of rights should be introduced as well, down to smaller issues that were a matter of technicality or were not really issues at all to begin with. Some people didn't want to sign it even after the amends, but it wasn't a big deal since it eventually got ratified and became the constitution. 

Answer 2

Not all the delegates who attended the convention signed the Constitution. ... Three delegates—Elbridge Gerry of Massachusetts and Edmund Randolph and George Mason of Virginia—were dissatisfied with the final document and refused to ink their signatures. 6. “We the People of the United States” was a late change.

Of the 55 original delegates, only 41 were present on September 17, 1787, to sign the proposed Constitution. Three of those present (George Mason and Edmund Randolph of Virginia and Elbridge Gerry of Massachusetts) refused to sign what they considered a flawed document.