Crank and pulley issues

When I try to start my truck, I can turn it see the
torque converter, flex plate spin as the should but
the pulleys don’t spin. I recently removed the duster
cover to find one of my flex plate bolts to be loose
and moving around inside the bell house (luckily
none of the important components like the the
starter and the torque converter teeth are damaged)
but I’m stumped as to what would be the cause of
a seemingly free spinning crank and flywheel.