Hi Everyone
I thought I'd post this in the hope I help someone.
I've recently had an issue whereby my activities recorded on my Edge 500 stopped being uploaded to Garmin Connect. I found a forum post suggesting I remove my device from Garmin Express and re-add it. I removed the device (so I effectively made Garmin Express 'forget' it) and then I attempted to re-add it. At this point it found the device, showed a picture of it and the serial number, but advised that 'this device is not compatible with Garmin Express'. I tried rebooting the Mac, and also ensuring that Garmin Express was up to date. I also tried to fully remove Garmin Express and install a fresh copy. All to no avail.
I spoke to Garmin support who had me basically repeat the steps which I had already performed. They then had me delete the device xml file, which again didn't help. Finally, they asked me to send them the device.xml along with the error reports from Garmin Express. Following this they told me my device was broken and that I should buy a replacement from them!
Last night I removed all of the activities from the 500 and temporarily held them on my Mac. I restored the Edge to factory settings and then low and behold, Garmin Express happily added it. I then re-added my activities and they synced to Garmin Connect and Strava as usual.
Bottom line, try a factory reset! Hopefully this will help someone.
Thanks.