On my Smartcode 909/910, the Status LED is solid red after the door handing process.
The lock interior is not mounted perpendicular to the ground. Remount lock interior assembly as illustrated in the Installation Guide.
The hole in the door is misaligned. Disassemble the lock, and reinstall it without the adapter ring on the exterior side of the door.
The latch is installed upside down. See page 8 here.
The battery level is too low. This is indicated by the keypad flashing red three times with three beeps. Use a fresh set of batteries, and perform the door handing process again.
The latch and strike are misaligned, causing the latch to bind.
If you have not already done so, perform the door handing process while the door is open. If it is successful only when the door is open, the latch and strike are not aligned as they should be. Ensure door preparation is in accordance with the door drilling instructions, available online.