Can't add my Garmin Edge 705 to Garmin Express

Have you tried a different cable?  Also make sure it is the correct type of cable.  Generally, there are two types of cables;

1. Charging cables only charge your device but cannot transfer data. These are commonly called “Charge-only” cables.
2. Data cables charge and transfer data.

thank you for your answer. I've tried 4 different cables.  When I plug the cable into the computer, the garmin edge turns on and says Saving History 0% but nothing happens.  When I plug it in to a plug socket it just charges.

It does when I hold the thumb button up (I found the article this morning). One one of the laptops it shows up but still nothing on Garmin express. On the other two laptops (older) I get a windows box saying it needs to be formatted before it can be used. Wasn’t sure what to do with that!

If you expand the link I provided earlier, and specifically the content about Windows and an Edge 705, you get the detailed instructions below.  Note that based on the exact wording, while holding the "Thumb Stick in UP position" (not having a 705, I'm not sure what this means) you plug the device into the computer and then wait "for up to 30 seconds."  Good luck!

Instructions for Edge devices

 Disconnect the device from the computer.

 Power the device off.

 Press and hold the appropriate button(s).

 Edge 605 and 705: Hold Thumb Stick in UP position.

 Plug the device into the computer.

 Wait until the device is recognized by the computer (may take up to 30 seconds).

 If prompted, install USB device drivers:

 Select "No, not at this time".

 Select Next.

 Select Install USB drivers automatically (Recommended).

 Select Next and wait for the USB driver installation to complete.

 Select Finish.

 Release appropriate button(s).

 Sync history and update the device firmware if not up to date using Garmin Express.

 Right-click on the device drive.

 Select Eject.

 Disconnect the device from the computer.

 Power on the device (wait for the firmware update to complete if installed).

 If you continue to have an issue with your device being recognized, contact Product Support.

Thank you for this.  sorry, I didn't get the message as I'd been logged out (but appeared logged in on the screen!). I had seen that and tried all of that, so will contact Product Support.  Thank you and sorry for the delayed response.