Mount the handle near the end of the the spindle on the spindle opposite the one that contains the larger flat ie.
Thru spindle too short on door handle.
If that does not work try and use a thin scraper or similar to disengage the latch from the gap between door and frame.
I do this most days easiest way to do it is to insert follower bar thats the technical term for the spindle into the door handle and through the latch in the door ensure door handle is.
Try and use a big flat screw driver to open the door where the spindle use to go.
Push on the handle until it fits against the corresponding trim plate at that side of.
Hold the knob in one hand and insert the other end of the spindle into the square port inside the door lock.
Remove the set screw securing the doorknob to the spindle then unscrew the door knob off of the spindle.
Remove the rosette off of the spindle.
The other end of the spindle and opposite knob is threaded so that this knob can screw on to the spindle and subsequently adjust for door thickness.
It s nice being able to get through your door without too much trouble.
Unscrew one handle and remove the spindle.
It seems the original had broken so it actually was too short to fit where it belonged.
Once door is open remove old latch and replace.
Take old latch with you as there are numerous different sizes.