Many of us have had issues over the years with Google Earth no longer working from Basecamp. I found a solution that works for me. It seems that Basecamp is a 32 bit program. It seems that the latest versions of Google Earth auto installs as a 64 bit program if your OS is 64 bit. If this is the case the two will not play nice together. Uninstall Google Earth and install the 32 bit version from https://support.google.com/earth/answer/168344?vid=0-17009934511-1520439167435 and see if it works for you. I tried the various command line register commands with no luck but this worked for me.
Ashley