---
title: "CO2 Laser: Keypad Says \"File Invalid\" or \"Communication Error,\" or LightBurn Keeps Disconnecting"
description: "Fix keypad \"File Invalid\" / \"Communication error\" messages and LightBurn disconnects on SA Laser CO2 machines: one LightBurn window, USB cable and port, clearing controller files, FTDI driver."
---

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# CO2 Laser: Keypad Says "File Invalid" or "Communication Error," or LightBurn Keeps Disconnecting

If your CO2 laser shows **"File Invalid"** or **"Communication error"** when you press **File** on the keypad after sending a job, or LightBurn keeps dropping from **Ready** to **Disconnected** (sometimes with an error), the laser and your computer are having trouble talking to each other. On our CO2 machines this is almost always the USB connection, the driver, or a controller that's full of old job files. Work through the checks below in order.

### Before you start: what changed?

Think about what was different right before this started: a new computer, a LightBurn update, a new or moved USB cable, a different USB port or hub, or the machine being moved. That's usually where the answer is.

### Check 1: Only one LightBurn window

LightBurn can only talk to one laser per window. If two LightBurn windows are open, one takes over the connection and the other shows **Disconnected**.

1. Close every LightBurn window.
2. Open LightBurn once and check the top of the **Laser** window. It should say **Ready**.

### Check 2: The USB cable and port

1. Unplug the USB cable at both ends and plug it back in firmly. On the laser, the USB plugs into the controller connection on the **bottom of the right-side panel**.
2. Plug straight into your computer, not through a hub or extension, and try a different USB port on the computer.
3. Blow out both cable ends with a small can of compressed air.
4. Look over the cable for frays, kinks, bends, or cuts.
5. If the errors keep coming back, swap in a different USB cable and test again.

### Check 3: Clear the job files stored on the laser

Every job you **Send** to the keypad is saved on the laser's controller. When a lot of files build up, the keypad can show errors or even freeze when you press **File**. You can clear them from LightBurn:

1. Make sure the laser is on and LightBurn shows **Ready**.
2. Open the **File List** tab (upper right, behind the Cuts/Layers window). If you don't see it, go to **Window → File List**.
3. Click **Refresh** to load the files saved on the laser.
4. Select files you no longer need and click **Delete**, starting from the **bottom** of the list (deleting from the top can take a long time), or click **Delete All Files** to clear everything.
5. Send your job again and try **File** on the keypad.

Deleted files can't be recovered, so keep a copy of any job you want on your computer first.

### Check 4: Reinstall the FTDI driver

CO2 lasers connect through the FTDI serial driver that installs with LightBurn. If it's missing or damaged (often after a new computer or a Windows update), LightBurn won't stay connected.

1. Close LightBurn.
2. Run the LightBurn installer again.
3. During setup, check the box for **Install FTDI serial driver (used by DSP's)**.
4. Restart LightBurn and confirm it shows **Ready**.

### Still getting errors?

Contact SA Laser Support at **888-964-3568** or **customerservice@salasers.com** (Mon–Fri, 9–5 CT). Please include:

- Your machine model and serial number
- The exact message on the keypad or in LightBurn (a photo is best)
- Your LightBurn version
- Which of the checks above you've already tried

### Related articles

- [Finding and Connecting Your Laser in LightBurn for CO2 Lasers](https://support.salasers.com/finding-and-connecting-your-laser-in-lightburn-for-co2-lasers?hsLang=en)
- [Configuring a Ruida Controller: A Step-by-Step Guide](https://support.salasers.com/configuring-ruida-controller?hsLang=en)
- [LightBurn User Guide: File List Window](https://docs.lightburnsoftware.com/2.2/Reference/FileListWindow/)

 

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