If you have an old Garmin GPS unit like a Garmin 276csx and have a computer with a Windows 7, 8 or later operating system, then your PC won’t detect the GPS as it’s too old for the operating system. This applies to the newer Macintosh operating system Maverick as well.

If you can’t detect the GPS on your PC / MAC whilst having one of the latest GPS units and operating systems, try to install Garmin USB drivers from Garmin’s website:

http://www8.garmin.com/support/agree.jsp?id=591

If you have upgraded to Windows 11:

It is apparent that the device drivers in Win11 do not include that which is needed for the old 276c device.

You can try this: Follow these steps:

1) Download the latest USB Drivers Software: Garmin: USB Drivers Updates & Downloads

2) Install the latest web updater: https://www8.garmin.com/support/download_details.jsp?id=931

after installing both of these and doing a restart, BASECAMP should now recognise the 276c (note Not the 276cx).