Originally Posted by retrocats
In other words, it looks like the shaft is not long enough. Also, you have to push in on the outside knob to get it to engage.
Most likely this is the problem. However, since the inside knob(lever) spins around there appears to be more of a problem. Did all the correct pieces get installed.
A few years ago I installed a new door knob. My original would no longer lock. You could just push a little and turn firmly. Not the safest way to travel.
Ever since then I also have had to push on my door to get the lock to firmly latch. Either my door has shrunk (not an impossibility), changed it's shape (very likely) and, or the striker is not long enough.
Try starting over taking extra care to make sure the whole assembly is as far toward the appropriate side as possible. There is usually at least 1/8" play, sometimes more.
Good luck, hope this helped a little.