Driveshaft won't fit

Did you have any trouble installing the rear mount. If yes,
check your rear mount to be sure it's in the factory position.
If no, I'm out.
unless the slip yoke is bottoming on the output shaft which, for some reason, has been pushed to the rear, like what happens when one of the clutches is not properly engaged on a planetary ........................
but, I can't see this as a thing if only the VB was changed.