When your K400 isn't working, the problem is likely a lost connection. The connection between the keyboard and the Unifying receiver can be lost for several reasons, such as:
- Low battery levels.
- Moving the receiver from one USB port to another.
- Moving the receiver to another computer.
- Plugging the receiver into a USB hub, KVM switch or other unsupported device. (NOTE: Your Unifying receiver must be plugged directly into your computer.)
- Using your keyboard on metal surfaces.
- Radio frequency (RF) interference from other sources, such as:
- Wireless speakers
- Computer power supplies
- Cell phones
- Garage door openers
Before connecting your keyboard:
Fix or rule out the potential problems listed above.
Insert new batteries (see answer 360023242574 for instructions).
Turn your keyboard on (see answer 360023242574 for instructions).
Make sure the receiver is securely plugged directly into a working USB port on your computer.
Turn your computer on.
Reconnecting your keyboard
Download and install the correct version of Logitech SetPoint Mouse and Keyboard Software from the K400 from the K400 Downloads Page.
- Launch the Logitech Unifying Software:
Windows: Start > Programs > Logitech > Unifying > Logitech Unifying Software
- Click Next at the bottom of the Welcome screen.
- Follow the on-screen instructions to turn your keyboard off and then back on.
When your keyboard is detected, you'll see this window:
If you can type in the testing box, select Yes and then click Next. Otherwise, repeat from step #4.
Click Finish to exit the Logitech Unifying Software. Your keyboard should now be connected.
If your keyboard frequently stops working and you keep having to reconnect it with the Unifying receiver, try these suggestions:
Keep other electrical devices at least 8 inches (20 cm) away from the receiver.
Move the keyboard closer to the receiver.
Try the receiver in a different USB port on your computer.