So without more details, this is a shot in the dark.
Some things to check:
Select the pipe that you want a bend to go, look at the top left of your ribbon and see if there's a check to the box that says "add bends automatically"
Select the pipe that you want a bend to go, right click, part properties, look at the connections. Remember the name if anything is there, and go to your prospector, select the part, see if it shows up, grips and all. If so, that's a display issue where cad might be drawing the part with the centerline. Go to the display tab and play around there.
IF it's there, it might be on a frozen layer. But that's baby stuff. If you can select it, but it's not showing up and all that, you might make sure the part list is headed to the right spot. That's easily accessible from your network properties.
If it's more than just one part that's not showing, like all of them, try the commands reconnectnetwork and regenpressuresolid. Regen after both seperately.
